Jupyter（IPython）

Jupyter Console

Jupyter控制台，原名IPython是一个增强的Python解释器。在之前的shell中我们是利用Python解释器来执行我们的Python脚本文件，而Jupyter加强了这个shell，并添加了一些细节，简化处理数据。

通常在你写数据分析脚本时或者编写原型代码时，你需要快速测试一些代码，此时你会在shell环境下执行它，因为这样很快速。Jupyter console与Jupyter notebook 最大的区别是console是在交互模式下运行。当你输入一行代码，他就会立刻执行，然后你会看到结果。如果你想写中篇的代码片断或做数据集的深入探索，Jupyter notebook会更好。如果你想要你写测试代码，或运行快速命令，Jupyter console会更好。

Jupyter项目正处于IPython向Jupyter重塑的过程中，输入jupyter console或者ipython 即可访问jupyter控制台。

~$ ipython
Python 3.4.3 (default, Oct 14 2015, 20:28:29)
Type "copyright", "credits" or "license" for more information.

IPython 3.2.1 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: print(10)
10

In [2]: exit

Getting Help

Jupyter 控制台有很丰富的內建帮助系统：

You can type ? after starting the console. This will display help about Jupyter. You can exit by typing q.

You can type %quickref. This is a magic that will tell you some useful commands.

If you want information about a variable, just type the name of the variable, followed by ?. ——var?

Type help() to get access to Python help. This will enable you to get help on all the modules and functions currently available. You can quit by typing quit.

If you want to use the Python help system to get information on a variable, type help(variable_name).——help(var)

In [3]: dq=5

In [4]: dq?
Type:        int
String form: 5
Docstring:
int(x=0) -> integer
int(x, base=10) -> integer

Convert a number or string to an integer, or return 0 if no arguments
are given.  If x is a number, return x.__int__().  For floating point
numbers, this truncates towards zero.

If x is not a number or if base is given, then x must be a string,
bytes, or bytearray instance representing an integer literal in the
# 输入q退出
In [5]: help(dq)
# 输入quit退出
# 输入exit退出Jupyter

Persistent Sessions

与 Jupyter notebook一样，当你第一次加载Jupyter console时会启动一个内核会话（kernel session）。每次在控制台中运行代码时，将会把变量存储在这个会话中，使得你下面运行的代码可以访问这些变量。

~$ ipython
Python 3.4.3 (default, Oct 14 2015, 20:28:29)
Type "copyright", "credits" or "license" for more information.

IPython 3.2.1 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

~$ ipython
Python 3.4.3 (default, Oct 14 2015, 20:28:29)
Type "copyright", "credits" or "license" for more information.

IPython 3.2.1 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: dq = 5

In [2]: dq_10 = dq * 10

In [3]: exit

Jupyter Magics

%quickref是 Jupyter种一种特殊的命令（Magics ），总是以% 开头，它们使你能够在Python没有执行你的命令前访问Jupyter的特殊功能。下面是一些特殊的magics ：

%run – allows you to run an external Python script. Any variables in the script will be stored in the current kernel session.

%edit – opens a file editor. Any code you type into the editor will be executed by Jupyter when you exit the editor.

%debug – if there’s an error in any of your code, running %debug afterwards will open an interactive debugger you can use to trace the error.

%history – shows you the last few commands you ran.

%save – saves the last few commands you ran to a file.

%who – print all the variables in the session.

%reset – resets the session, and removes all stored variables.

# 新建一个zm.py的脚本，添加了一个变量，一个打印语句
if __name__=="__main__":
zm = "ZM is a good programmer"
print(zm)

在ipython中使用%run执行这个文本，使用%who来查看变量：

In [1]: %run zm.py
ZM is a good programmer
In [2]: %who
zm

在使用%who查看变量之前，首先要是有%run来执行一个脚本，然后%who显示的就是刚刚执行的那个脚本中的变量。

Autocompletion

Autocompletion（自动补全）：当你输入一个变量名称时，按TAB键可以自动匹配所有的变量，自动补全剩余的字符。If you hit TAB after typing a variable name, Jupyter will show you the methods on the variable.

# 输入字母a之后按TAB键，自动回车显示所有匹配的变量名以及函数名
In [1]: a
%alias        %autoindent   all           as
%alias_magic  %automagic    and           ascii
%autocall     abs           any           assert

Accessing The Shell

可以在Jupyter 中运行shell命令，只要在命令的前面加上！就可以。比如！ls会显示当前Jupyter 所在目录的所有文件：

In [1]: !ls

In [2]: !whoami
dq

In [3]: !ls -a
.  ..  .bashrc  .byobu  .cache  .ipython  .tmux.conf

In [4]:

Pasting In Code

在python采用复制时不会复制缩进，因此粘贴时会出现错误。因此需要使用paste magics：

%cpaste – opens a special editing area where you can paste in code normally, without whitespace being a problem. You can type –

alone on a line to exit. After you exit, any code you pasted in will

be immediately executed.

%paste – takes code from your clipboard and runs it in Jupyter. This doesn’t work on remote systems, where Jupyter doesn’t

have access to your clipboard.

# 首先将下面这段代码复制到剪切板
for i in range(10):
if i < 5:
print(i)
else:
print(i * 2)
# 打开ipython，然后在其中输入%cpaste
# 再输入--退出时你的程序就会被执行。

Next Steps

Some specific explorations you can try:

Explore more of the magics.

Try using Jupyter to debug exceptions.

Develop a Python script locally, and see if Jupyter can help with your workflow.