Python2到Python3代码的转换工具2to3.py

之前一直遇到Python2代码转到Python3代码的需求，最近才知道Python官方就有一个转换工具：2to3.py。 
无论是Python官网下载安装的python还是利用Anaconda安装，目录都在{Python_HOME}\Tools\scripts里面。运行 2to3.py 脚本，打印如下：

python 2to3.py --help
Usage: 2to3 [options] file|dir ...

Options:
-h, --help            show this help message and exit
-d, --doctests_only   Fix up doctests only
-f FIX, --fix=FIX     Each FIX specifies a transformation; default: all
-j PROCESSES, --processes=PROCESSES
Run 2to3 concurrently
-x NOFIX, --nofix=NOFIX
Prevent a transformation from being run
-l, --list-fixes      List available transformations
-p, --print-function  Modify the grammar so that print() is a function
-v, --verbose         More verbose logging
--no-diffs            Don't show diffs of the refactoring
-w, --write           Write back modified files
-n, --nobackups       Don't write backups for modified files
-o OUTPUT_DIR, --output-dir=OUTPUT_DIR
Put output files in this directory instead of
overwriting the input files.  Requires -n.
-W, --write-unchanged-files
Also write files even if no changes were required
(useful with --output-dir); implies -w.
--add-suffix=ADD_SUFFIX
Append this string to all output filenames. Requires
-n if non-empty.  ex: --add-suffix='3' will generate

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假设我在E:\pycode目录下有个py2.py文件，代码如下：

print 'test'

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我想把上面的代码改成python3版本的。、 
应该先cmd进入{Python_HOME}\Tools\scripts目录，然后执行如下：

python 2to3.py -w E:\pycode\py2.py

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执行整个流程如下：

D:\Anaconda3\Tools\scripts>python 2to3.py -w E:\pycode\py2.py
RefactoringTool: Skipping optional fixer: buffer
RefactoringTool: Skipping optional fixer: idioms
RefactoringTool: Skipping optional fixer: set_literal
RefactoringTool: Skipping optional fixer: ws_comma
RefactoringTool: Refactored E:\pycode\py2.py
--- E:\pycode\py2.py    (original)
+++ E:\pycode\py2.py    (refactored)
@@ -1 +1 @@
-print 'test'
+print('test')
RefactoringTool: Files that were modified:
RefactoringTool: E:\pycode\py2.py

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然后我们可以看到，在E:\pycode目录下多了一个py2.py.bak文件，这是原来的py2.py文件备份。 
查看py2.py，内容已被修改为：

print('test')