理解Python的With语句
2016-08-12 17:09
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<div class="p" style="margin: 0px; padding: 0px 0px 14px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;"><h2 style="margin: 8px 0px 0px; padding: 30px 0px 0px; border-width: 1px 0px 0px; border-top-style: dashed; border-top-color: rgb(221, 221, 221); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"><a target=_blank target="_blank" name="h20" href="http://python.42qu.com/11155501#h20" style="color: rgb(0, 0, 0); text-decoration: none; margin: 0px; padding: 0px 0px 0px 27px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; outline: none; background-color: transparent;">With语句是什么？</a></h2> Python’s with statement provides a very convenient way of dealing with the situation where you have to do a setup and teardown to make something happen. A very good example for this is the situation where you want to gain a handler to a file, read data from the file and the close the file handler. 有一些任务，可能事先需要设置，事后做清理工作。对于这种场景，Python的with语句提供了一种非常方便的处理方式。一个很好的例子是文件处理，你需要获取一个文件句柄，从文件中读取数据，然后关闭文件句柄。 Without the with statement, one would write something along the lines of: 如果不用with语句，代码如下：<div class="codesh" style="margin: 14px 0px; padding: 0px; border: 1px dotted rgb(204, 204, 204); font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div id="highlighter_795190" class="syntaxhighlighter python" style="padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden; margin: 1em 0px !important; font-size: 1em !important; position: relative !important; overflow-x: auto !important;"><table border="0" cellpadding="0" cellspacing="0" style="font-variant: inherit; border-collapse: collapse; border-spacing: 0px; width: 616px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><tbody style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><tr style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><td class="gutter" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(175, 175, 175) !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">1</div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">2</div><div class="line number3 index2 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">3</div></td><td class="code" style="font-variant: inherit; width: 584px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><div class="container" style="padding-bottom: 0px; font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding-top: 0px !important; padding-right: 0px !important; padding-left: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: relative !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">file</code> <code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">=</code> <code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">open</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">(</code><code class="python string" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: blue !important;">"/tmp/foo.txt"</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">)</code></div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">data </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">=</code> <code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">file</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">.read()</code></div><div class="line number3 index2 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">file</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">.close()</code></div></div></td></tr></tbody></table></div></div></div>There are two annoying things here. First, you end up forgetting to close the file handler. The second is how to handle exceptions that may occur once the file handler has been obtained. One could write something like this to get around this: 这里有两个问题。一是可能忘记关闭文件句柄；二是文件读取数据发生异常，没有进行任何处理。下面是处理异常的加强版本：<div class="codesh" style="margin: 14px 0px; padding: 0px; border: 1px dotted rgb(204, 204, 204); font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div id="highlighter_485254" class="syntaxhighlighter python" style="padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden; margin: 1em 0px !important; font-size: 1em !important; position: relative !important; overflow-x: auto !important;"><table border="0" cellpadding="0" cellspacing="0" style="font-variant: inherit; border-collapse: collapse; border-spacing: 0px; width: 616px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><tbody style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><tr style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><td class="gutter" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(175, 175, 175) !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">1</div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">2</div><div class="line number3 index2 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">3</div><div class="line number4 index3 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">4</div><div class="line number5 index4 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">5</div></td><td class="code" style="font-variant: inherit; width: 584px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><div class="container" style="padding-bottom: 0px; font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding-top: 0px !important; padding-right: 0px !important; padding-left: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: relative !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">file</code> <code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">=</code> <code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">open</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">(</code><code class="python string" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: blue !important;">"/tmp/foo.txt"</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">)</code></div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">try</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">:</code></div><div class="line number3 index2 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">data </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">=</code> <code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">file</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">.read()</code></div><div class="line number4 index3 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">finally</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">:</code></div><div class="line number5 index4 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">file</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">.close()</code></div></div></td></tr></tbody></table></div></div></div>While this works well, it is unnecessarily verbose. This is where with is useful. The good thing about with apart from the better syntax is that it is very good handling exceptions. The above code would look like this, when using with: 虽然这段代码运行良好，但是太冗长了。这时候就是with一展身手的时候了。除了有更优雅的语法，with还可以很好的处理上下文环境产生的异常。下面是with版本的代码：<div class="codesh" style="margin: 14px 0px; padding: 0px; border: 1px dotted rgb(204, 204, 204); font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div id="highlighter_99052" class="syntaxhighlighter python" style="padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden; margin: 1em 0px !important; font-size: 1em !important; position: relative !important; overflow-x: auto !important;"><table border="0" cellpadding="0" cellspacing="0" style="font-variant: inherit; border-collapse: collapse; border-spacing: 0px; width: 616px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><tbody style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><tr style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><td class="gutter" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(175, 175, 175) !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">1</div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">2</div></td><td class="code" style="font-variant: inherit; width: 584px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><div class="container" style="padding-bottom: 0px; font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding-top: 0px !important; padding-right: 0px !important; padding-left: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: relative !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">with </code><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">open</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">(</code><code class="python string" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: blue !important;">"/tmp/foo.txt"</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">) as </code><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">file</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">:</code></div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">data </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">=</code> <code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">file</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">.read()</code></div></div></td></tr></tbody></table></div></div></div><h2 style="margin: 8px 0px 0px; padding: 30px 0px 0px; border-width: 1px 0px 0px; border-top-style: dashed; border-top-color: rgb(221, 221, 221); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"><a target=_blank name="t1" style="color: rgb(106, 57, 6);"></a><a target=_blank target="_blank" name="h21" href="http://python.42qu.com/11155501#h21" style="color: rgb(0, 0, 0); text-decoration: none; margin: 0px; padding: 0px 0px 0px 27px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; outline: none; background-color: transparent;">with如何工作？</a></h2> while this might look like magic, the way Python handles with is more clever than magic. The basic idea is that the statement after with has to evaluate an object that responds to an __enter__() as well as an __exit__() function. 这看起来充满魔法，但不仅仅是魔法，Python对with的处理还很聪明。基本思想是with所求值的对象必须有一个__enter__()方法，一个__exit__()方法。 After the statement that follows with is evaluated, the __enter__() function on the resulting object is called. The value returned by this function is assigned to the variable following as. After every statement in the block is evaluated, the __exit__() function is called. 紧跟with后面的语句被求值后，返回对象的__enter__()方法被调用，这个方法的返回值将被赋值给as后面的变量。当with后面的代码块全部被执行完之后，将调用前面返回对象的__exit__()方法。 This can be demonstrated with the following example: 下面例子可以具体说明with如何工作：<div class="codesh" style="margin: 14px 0px; padding: 0px; border: 1px dotted rgb(204, 204, 204); font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div id="highlighter_980932" class="syntaxhighlighter python" style="padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden; margin: 1em 0px !important; font-size: 1em !important; position: relative !important; overflow-x: auto !important;"><table border="0" cellpadding="0" cellspacing="0" style="font-variant: inherit; border-collapse: collapse; border-spacing: 0px; width: 616px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><tbody style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><tr style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><td class="gutter" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(175, 175, 175) !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">1</div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">2</div><div class="line number3 index2 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">3</div><div class="line number4 index3 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">4</div><div class="line number5 index4 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">5</div><div class="line number6 index5 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">6</div><div class="line number7 index6 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">7</div><div class="line number8 index7 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">8</div><div class="line number9 index8 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">9</div><div class="line number10 index9 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">10</div><div class="line number11 index10 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">11</div><div class="line number12 index11 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">12</div><div class="line number13 index12 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">13</div><div class="line number14 index13 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">14</div><div class="line number15 index14 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">15</div><div class="line number16 index15 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">16</div><div class="line number17 index16 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">17</div><div class="line number18 index17 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">18</div><div class="line number19 index18 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">19</div></td><td class="code" style="font-variant: inherit; width: 576px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><div class="container" style="padding-bottom: 0px; font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding-top: 0px !important; padding-right: 0px !important; padding-left: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: relative !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python comments" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 130, 0) !important;">#!/usr/bin/env python</code></div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python comments" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 130, 0) !important;"># with_example01.py</code></div><div class="line number3 index2 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"> </div><div class="line number4 index3 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"> </div><div class="line number5 index4 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">class</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">Sample:</code></div><div class="line number6 index5 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">def</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">__enter__(</code><code class="python color1" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: gray !important;">self</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">):</code></div><div class="line number7 index6 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">print</code> <code class="python string" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: blue !important;">"In __enter__()"</code></div><div class="line number8 index7 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">return</code> <code class="python string" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: blue !important;">"Foo"</code></div><div class="line number9 index8 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"> </div><div class="line number10 index9 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">def</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">__exit__(</code><code class="python color1" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: gray !important;">self</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">, </code><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">type</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">, value, trace):</code></div><div class="line number11 index10 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">print</code> <code class="python string" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: blue !important;">"In __exit__()"</code></div><div class="line number12 index11 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"> </div><div class="line number13 index12 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"> </div><div class="line number14 index13 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">def</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">get_sample():</code></div><div class="line number15 index14 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">return</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">Sample()</code></div><div class="line number16 index15 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"> </div><div class="line number17 index16 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"> </div><div class="line number18 index17 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">with get_sample() as sample:</code></div><div class="line number19 index18 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">print</code> <code class="python string" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: blue !important;">"sample:"</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">, sample</code></div></div></td></tr></tbody></table></div></div></div>When executed, this will result in: 运行代码，输出如下<div class="codesh" style="margin: 14px 0px; padding: 0px; border: 1px dotted rgb(204, 204, 204); font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div id="highlighter_497800" class="syntaxhighlighter python" style="padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden; margin: 1em 0px !important; font-size: 1em !important; position: relative !important; overflow-x: auto !important;"><table border="0" cellpadding="0" cellspacing="0" style="font-variant: inherit; border-collapse: collapse; border-spacing: 0px; width: 616px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><tbody style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><tr style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><td class="gutter" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(175, 175, 175) !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">1</div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">2</div><div class="line number3 index2 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">3</div><div class="line number4 index3 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">4</div></td><td class="code" style="font-variant: inherit; width: 584px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><div class="container" style="padding-bottom: 0px; font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding-top: 0px !important; padding-right: 0px !important; padding-left: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: relative !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">bash</code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">-</code><code class="python value" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 153, 0) !important;">3.2</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">$ .</code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">/</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">with_example01.py</code></div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">In __enter__()</code></div><div class="line number3 index2 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">sample: Foo</code></div><div class="line number4 index3 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">In __exit__()</code></div></div></td></tr></tbody></table></div></div></div>As you can see, The __enter__() function is executed The value returned by it - in this case "Foo" is assigned to sample The body of the block is executed, thereby printing the value of sample ie. "Foo" The __exit__() function is called. What makes with really powerful is the fact that it can handle exceptions. You would have noticed that the __exit__() function for Sample takes three arguments - val, type and trace. These are useful in exception handling. Let’s see how this works by modifying the above example. 正如你看到的， 1. __enter__()方法被执行 2. __enter__()方法返回的值 - 这个例子中是"Foo"，赋值给变量'sample' 3. 执行代码块，打印变量"sample"的值为 "Foo" 4. __exit__()方法被调用 with真正强大之处是它可以处理异常。可能你已经注意到Sample类的__exit__方法有三个参数- val, type 和 trace。 这些参数在异常处理中相当有用。我们来改一下代码，看看具体如何工作的。<div class="codesh" style="margin: 14px 0px; padding: 0px; border: 1px dotted rgb(204, 204, 204); font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div id="highlighter_344046" class="syntaxhighlighter python" style="padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden; margin: 1em 0px !important; font-size: 1em !important; position: relative !important; overflow-x: auto !important;"><table border="0" cellpadding="0" cellspacing="0" style="font-variant: inherit; border-collapse: collapse; border-spacing: 0px; width: 616px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><tbody style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><tr style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><td class="gutter" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(175, 175, 175) !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">1</div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">2</div><div class="line number3 index2 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">3</div><div class="line number4 index3 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">4</div><div class="line number5 index4 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">5</div><div class="line number6 index5 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">6</div><div class="line number7 index6 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">7</div><div class="line number8 index7 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">8</div><div class="line number9 index8 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">9</div><div class="line number10 index9 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">10</div><div class="line number11 index10 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">11</div><div class="line number12 index11 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">12</div><div class="line number13 index12 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">13</div><div class="line number14 index13 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">14</div><div class="line number15 index14 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">15</div><div class="line number16 index15 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">16</div><div class="line number17 index16 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">17</div><div class="line number18 index17 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">18</div><div class="line number19 index18 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">19</div></td><td class="code" style="font-variant: inherit; width: 576px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><div class="container" style="padding-bottom: 0px; font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding-top: 0px !important; padding-right: 0px !important; padding-left: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: relative !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python comments" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 130, 0) !important;">#!/usr/bin/env python</code></div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python comments" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 130, 0) !important;"># with_example02.py</code></div><div class="line number3 index2 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"> </div><div class="line number4 index3 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"> </div><div class="line number5 index4 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">class</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">Sample:</code></div><div class="line number6 index5 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">def</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">__enter__(</code><code class="python color1" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: gray !important;">self</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">):</code></div><div class="line number7 index6 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">return</code> <code class="python color1" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: gray !important;">self</code></div><div class="line number8 index7 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"> </div><div class="line number9 index8 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">def</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">__exit__(</code><code class="python color1" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: gray !important;">self</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">, </code><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">type</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">, value, trace):</code></div><div class="line number10 index9 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">print</code> <code class="python string" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: blue !important;">"type:"</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">, </code><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">type</code></div><div class="line number11 index10 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">print</code> <code class="python string" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: blue !important;">"value:"</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">, value</code></div><div class="line number12 index11 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">print</code> <code class="python string" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: blue !important;">"trace:"</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">, trace</code></div><div class="line number13 index12 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"> </div><div class="line number14 index13 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">def</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">do_something(</code><code class="python color1" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: gray !important;">self</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">):</code></div><div class="line number15 index14 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">bar </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">=</code> <code class="python value" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 153, 0) !important;">1</code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">/</code><code class="python value" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 153, 0) !important;">0</code></div><div class="line number16 index15 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">return</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">bar </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">+</code> <code class="python value" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 153, 0) !important;">10</code></div><div class="line number17 index16 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"> </div><div class="line number18 index17 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">with Sample() as sample:</code></div><div class="line number19 index18 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">sample.do_something()</code></div></div></td></tr></tbody></table></div></div></div>Notice how in this example, instead of get_sample(), with takes Sample(). It does not matter, as long as the statement that follows with evaluates to an object that has an __enter__() and __exit__() functions. In this case, Sample()’s __enter__() returns the newly created instance of Sample and that is what gets passed to sample. 这个例子中，with后面的get_sample()变成了Sample()。这没有任何关系，只要紧跟with后面的语句所返回的对象有__enter__()和__exit__()方法即可。此例中，Sample()的__enter__()方法返回新创建的Sample对象，并赋值给变量sample。 When executed: 代码执行后：<div class="codesh" style="margin: 14px 0px; padding: 0px; border: 1px dotted rgb(204, 204, 204); font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden;"><div id="highlighter_780198" class="syntaxhighlighter python" style="padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; overflow-y: hidden; margin: 1em 0px !important; font-size: 1em !important; position: relative !important; overflow-x: auto !important;"><table border="0" cellpadding="0" cellspacing="0" style="font-variant: inherit; border-collapse: collapse; border-spacing: 0px; width: 616px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><tbody style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><tr style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><td class="gutter" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(175, 175, 175) !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">1</div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">2</div><div class="line number3 index2 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">3</div><div class="line number4 index3 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">4</div><div class="line number5 index4 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">5</div><div class="line number6 index5 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">6</div><div class="line number7 index6 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">7</div><div class="line number8 index7 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">8</div><div class="line number9 index8 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">9</div><div class="line number10 index9 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 0.5em 0px 1em !important; border-width: 0px 3px 0px 0px !important; border-right-style: solid !important; border-right-color: rgb(204, 204, 153) !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; text-align: right !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;">10</div></td><td class="code" style="font-variant: inherit; width: 576px; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; min-height: inherit !important;"><div class="container" style="padding-bottom: 0px; font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding-top: 0px !important; padding-right: 0px !important; padding-left: 0px !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: relative !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><div class="line number1 index0 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">bash</code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">-</code><code class="python value" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 153, 0) !important;">3.2</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">$ .</code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">/</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">with_example02.py</code></div><div class="line number2 index1 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">type</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">: <</code><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">type</code> <code class="python string" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: blue !important;">'exceptions.ZeroDivisionError'</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">></code></div><div class="line number3 index2 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">value: integer division </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">or</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">modulo by zero</code></div><div class="line number4 index3 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">trace: <traceback </code><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">object</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">at </code><code class="python value" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 153, 0) !important;">0x1004a8128</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">></code></div><div class="line number5 index4 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">Traceback (most recent call last):</code></div><div class="line number6 index5 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">File</code> <code class="python string" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: blue !important;">"./with_example02.py"</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">, line </code><code class="python value" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 153, 0) !important;">19</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">, </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">in</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"><module></code></div><div class="line number7 index6 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">sample.do_something()</code></div><div class="line number8 index7 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python functions" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(255, 20, 147) !important;">File</code> <code class="python string" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: blue !important;">"./with_example02.py"</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">, line </code><code class="python value" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 153, 0) !important;">15</code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">, </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">in</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">do_something</code></div><div class="line number9 index8 alt2" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python spaces" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;"> </code><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">bar </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">=</code> <code class="python value" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 153, 0) !important;">1</code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">/</code><code class="python value" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 153, 0) !important;">0</code></div><div class="line number10 index9 alt1" style="font-variant: inherit; overflow-y: hidden; margin: 0px !important; padding: 0px 1em !important; border: 0px !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow-x: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; white-space: pre !important;"><code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">ZeroDivisionError: integer division </code><code class="python keyword" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; font-weight: bold !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important; color: rgb(0, 102, 153) !important;">or</code> <code class="python plain" style="font-variant: inherit; margin: 0px !important; padding: 0px !important; border: 0px !important; font-family: Consolas, "Bitstream Vera Sans Mono", "Courier New", Courier, monospace !important; font-size: 1em !important; line-height: 1.1em !important; vertical-align: baseline !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; outline: 0px !important; overflow: visible !important; position: static !important; right: auto !important; top: auto !important; width: auto !important; min-height: inherit !important;">modulo by zero</code></div></div></td></tr></tbody></table></div></div></div>Essentially, if there are exceptions being thrown from anywhere inside the block, the __exit__() function for the object is called. As you can see, the type, value and the stack trace associated with the exception thrown is passed to this function. In this case, you can see that there was a ZeroDivisionError exception being thrown. People implementing libraries can write code that clean up resources, close files etc. in their __exit__() functions. 实际上，在with后面的代码块抛出任何异常时，__exit__()方法被执行。正如例子所示，异常抛出时，与之关联的type，value和stack trace传给__exit__()方法，因此抛出的ZeroDivisionError异常被打印出来了。开发库时，清理资源，关闭文件等等操作，都可以放在__exit__方法当中。 Thus, Python’s with is a nifty construct that makes code a little less verbose and makes cleaning up during exceptions a bit easier. 因此，Python的with语句是提供一个有效的机制，让代码更简练，同时在异常产生时，清理工作更简单。 I have put the code examples given here on <a target=_blank target="_blank" title="https://github.com/sdqali/python_dojo/tree/master/with" href="https://github.com/sdqali/python_dojo/tree/master/with" class="aT" rel="nofollow" style="color: rgb(0, 0, 0); text-decoration: none; margin: 0px; padding: 0px 0px 3px; border-width: 0px 0px 1px; border-bottom-style: dotted; border-bottom-color: rgb(0, 0, 0); font-family: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; outline: none;">Github</a>. 示例代码可以在<a target=_blank target="_blank" title="https://github.com/sdqali/python_dojo/tree/master/with" href="https://github.com/sdqali/python_dojo/tree/master/with" class="aT" rel="nofollow" style="color: rgb(0, 0, 0); text-decoration: none; margin: 0px; padding: 0px 0px 3px; border-width: 0px 0px 1px; border-bottom-style: dotted; border-bottom-color: rgb(0, 0, 0); font-family: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; outline: none;">Github</a>上面找到。 译注：本文原文见<a target=_blank target="_blank" title="http://blog.sdqali.in/blog/2012/07/09/understanding-pythons-with/" href="http://blog.sdqali.in/blog/2012/07/09/understanding-pythons-with/" class="aT" rel="nofollow" style="color: rgb(0, 0, 0); text-decoration: none; margin: 0px; padding: 0px 0px 3px; border-width: 0px 0px 1px; border-bottom-style: dotted; border-bottom-color: rgb(0, 0, 0); font-family: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; outline: none;">Understanding Python's "With" Statement</a></div>linbo（同济大学·计算机科学与技术系）
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