IPython使用技巧

前言

  我第一次接触 IPython 的时候是在《Python数据科学手册》中的第一章“IPython:超越Python”，之后就深深的喜欢上了IPython。为了感谢本书，这里推荐对数据分析感兴趣的可以看看这本书。

  IPython可以直接在命令行中使用，而我更喜欢的是jupyter notebook，一个基于IPython的网页版，两者使用完全一样，因为内核就是一个东西，但是jupyter notebook是基于网页版的，这样可以不受环境限制，只要能上网就可以使用，不管是windows、linux、mac、平板、甚至手机，只要可以打开浏览器就可以使用。还有一点很重要，可以白嫖。

  关于白嫖，在我知道jupyter notebook后，在自己服务器上搭建过环境，然后远程访问。但是后来发现很多的数据分析平台其实都有免费的。虽然都有限制，比如资源限制（内存、CPU）；比如代码包限制，比如百度现在已经不允许用pytorch；比如运行时长限制等。毕竟商业行为，如果实在需要就只能花钱了，毕竟自己买服务器也是要花钱的，除非你花大价钱，否则还真没有免费的配置高。

推荐

  上面说了白嫖，这里迫不及待的就推荐几个平台，有的可能需要科学上网。

• 百度 AI Studio：免费2核8G，更高配置需要花算力点，算力点可以买，也可以签到获得（很少就是了，但是攒一下，4核32G也可以用上俩小时）。最大的问题就是不能用除了百度自研的飞桨之外的其他机器学习包,基础的numpy等还是有的。
• 和鲸社区:这个平台好像换了好多次名字和网址。而且也已经没有免费资源了，但是他好像有免费点数（变了好多次不知道现在还有没有），这个平台是我找到的第一个国内平台。
• Google 的 colab:这个我想大家都知道如何访问。他的代码是存放在Google云盘的。
• 玻尔®️ 科研空间站:从广告点进去的，有免费资源，就是小了点。

  这些平台还提供各种学习资料及其他相关项目和数据，其实还有很多这样的平台，大部分都有免费资源或者通过签到、打卡、做任务获得免费资源。对于初学者应该很好了。如果实在需要更高资源，可能就要花钱了。

安装

  上面说了，IPyhton 和 jupyter notebook其实就是一个咚咚，都是通过ipykernel这个内核实现的。一个是命令行端，一个是网页端。而且他其实就是一个pip包。

IPyhton

# 安装
pip install ipython
# 运行
ipython

jupyter notebook

# 安装
pip install notebook
# 启动
jupyter notebook
# 启动后，浏览器就会自动打开，如果没有打开，可以手动打开 http://127.0.0.1:8888

IPython使用技巧

一、tab自动补齐

  用惯了linux命令的这个自然不用说，应该是很习惯的，就算没用过现在的主流编辑器也都是支持自动提示的。只有写一个首字母+tab 既可以得到提醒，再也不用发愁记那些方法属性的拼写了。所有这个必须是第一个。

二、？获取文档

  linux习惯了tab补齐命令，那遇到不会用的命令，咋办呢，-h、 --help、 man就应该是必不可少的。在IPython中这些都有，就是?、 ??。

• ?：前面啥也没有就直接?：打印IPython简介。按q退出
• 对象?：内省，可以打印出该变量的详细信息。按q退出
• 对象??：内省，打印源码，有时候也会不打印源码而是和上面一样，这是因为这个方法不是python写的。按q退出

三、history

  这个命令可以帮我们打印之前我们输入的命令。也可以用下划线方式获取历史输入和输出。

• _x：x表示输出行号，所有_3就是Out[3]
• _：表示上一次输出
• __：表示倒数第二次输出
• _ix：x表示行号，i表示input，所有_i3，就是In [3]

$ ipython
Python 3.10.13 (main, Sep 11 2023, 08:39:02) [Clang 14.0.6 ]
Type 'copyright', 'credits' or 'license' for more information
IPython 8.15.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: a=1+1

In [2]: a
Out[2]: 2

In [3]: b=a+1

In [4]: b
Out[4]: 3

In [5]: c=b+1

In [6]: c
Out[6]: 4

In [7]: history
a=1+1
a
b=a+1
b
c=b+1
c
history

In [8]: _
Out[8]: 4

In [9]: _6
Out[9]: 4

In [10]: _i7
Out[10]: 'history'

In [11]: __
Out[11]: 4

In [12]: exit

四、!、% 执行shell命令

  在IPython中，要执行系统命令，不需要退出，只要在命令前加!，其实可以更简单，不加大部分命令也是可以执行的。

$ ipython
Python 3.10.13 (main, Sep 11 2023, 08:39:02) [Clang 14.0.6 ]
Type 'copyright', 'credits' or 'license' for more information
IPython 8.15.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: pwd
Out[1]: '/Users/mmy83'

In [2]: !pwd
/Users/mmy83

In [3]: %pwd
Out[3]: '/Users/mmy83'

In [4]:

  通过上面的例子会发现，三者是不同的。直接执行命令其实是%方式执行的别名，而!执行是真的命令行执行。而且不是每一个命令都可以用这三者方式执行，比如cd,就不能用!方式执行，但是可以用%或者直接执行。因为cd或改变后续环境目录。反正我是优先直接执行，这样不行就换!方式。

%quickref 查看参考

  这个命令必须要单独说一下，因为上面说的这些东西，这个命令里面都有明确说明。

IPython -- An enhanced Interactive Python - Quick Reference Card
================================================================

obj?, obj??      : Get help, or more help for object (also works as
                   ?obj, ??obj).
?foo.*abc*       : List names in 'foo' containing 'abc' in them.
%magic           : Information about IPython's 'magic' % functions.

Magic functions are prefixed by % or %%, and typically take their arguments
without parentheses, quotes or even commas for convenience.  Line magics take a
single % and cell magics are prefixed with two %%.

Example magic function calls:

%alias d ls -F   : 'd' is now an alias for 'ls -F'
alias d ls -F    : Works if 'alias' not a python name
alist = %alias   : Get list of aliases to 'alist'
cd /usr/share    : Obvious. cd -<tab> to choose from visited dirs.
%cd??            : See help AND source for magic %cd
%timeit x=10     : time the 'x=10' statement with high precision.
%%timeit x=2**100
x**100           : time 'x**100' with a setup of 'x=2**100'; setup code is not
                   counted.  This is an example of a cell magic.

System commands:

!cp a.txt b/     : System command escape, calls os.system()
cp a.txt b/      : after %rehashx, most system commands work without !
cp ${f}.txt $bar : Variable expansion in magics and system commands
files = !ls /usr : Capture system command output
files.s, files.l, files.n: "a b c", ['a','b','c'], 'a\nb\nc'

History:

_i, _ii, _iii    : Previous, next previous, next next previous input
_i4, _ih[2:5]    : Input history line 4, lines 2-4
exec(_i81)       : Execute input history line #81 again
%rep 81          : Edit input history line #81
_, __, ___       : previous, next previous, next next previous output
_dh              : Directory history
_oh              : Output history
%hist            : Command history of current session.
%hist -g foo     : Search command history of (almost) all sessions for 'foo'.
%hist -g         : Command history of (almost) all sessions.
%hist 1/2-8      : Command history containing lines 2-8 of session 1.
%hist 1/ ~2/     : Command history of session 1 and 2 sessions before current.
%hist ~8/1-~6/5  : Command history from line 1 of 8 sessions ago to
                   line 5 of 6 sessions ago.
%edit 0/         : Open editor to execute code with history of current session.

Autocall:

f 1,2            : f(1,2)  # Off by default, enable with %autocall magic.
/f 1,2           : f(1,2) (forced autoparen)
,f 1 2           : f("1","2")
;f 1 2           : f("1 2")

Remember: TAB completion works in many contexts, not just file names
or python names.

The following magic functions are currently available:

%alias:
    Define an alias for a system command.
%alias_magic:
    ::
%autoawait:

%autocall:
    Make functions callable without having to type parentheses.
%autoindent:
    Toggle autoindent on/off (deprecated)
%automagic:
    Make magic functions callable without having to type the initial %.
%bookmark:
    Manage IPython's bookmark system.
%cat:
    Alias for `!cat`
%cd:
    Change the current working directory.
%clear:
    Alias for `!clear`
%code_wrap:
    ::
%colors:
    Switch color scheme for prompts, info system and exception handlers.
%conda:
    Run the conda package manager within the current kernel.
%config:
    configure IPython
%cp:
    Alias for `!cp`
%cpaste:
    Paste & execute a pre-formatted code block from clipboard.
%debug:
    ::
%dhist:
    Print your history of visited directories.
%dirs:
    Return the current directory stack.
%doctest_mode:
    Toggle doctest mode on and off.
%ed:
    Alias for `%edit`.
%edit:
    Bring up an editor and execute the resulting code.
%env:
    Get, set, or list environment variables.
%gui:
    Enable or disable IPython GUI event loop integration.
%hist:
    Alias for `%history`.
%history:
    ::
%killbgscripts:
    Kill all BG processes started by %%script and its family.
%ldir:
    Alias for `!ls -F -G -l %l | grep /$`
%less:
    Alias for `!less`
%lf:
    Alias for `!ls -F -l -G %l | grep ^-`
%lk:
    Alias for `!ls -F -l -G %l | grep ^l`
%ll:
    Alias for `!ls -F -l -G`
%load:
    Load code into the current frontend.
%load_ext:
    Load an IPython extension by its module name.
%loadpy:
    Alias of `%load`
%logoff:
    Temporarily stop logging.
%logon:
    Restart logging.
%logstart:
    Start logging anywhere in a session.
%logstate:
    Print the status of the logging system.
%logstop:
    Fully stop logging and close log file.
%ls:
    Alias for `!ls -F -G`
%lsmagic:
    List currently available magic functions.
%lx:
    Alias for `!ls -F -l -G %l | grep ^-..x`
%macro:
    Define a macro for future re-execution. It accepts ranges of history,
%magic:
    Print information about the magic function system.
%man:
    Alias for `!man`
%matplotlib:
    ::
%mkdir:
    Alias for `!mkdir`
%more:
    Alias for `!more`
%mv:
    Alias for `!mv`
%notebook:
    ::
%page:
    Pretty print the object and display it through a pager.
%paste:
    Paste & execute a pre-formatted code block from clipboard.
%pastebin:
    Upload code to dpaste.com, returning the URL.
%pdb:
    Control the automatic calling of the pdb interactive debugger.
%pdef:
    Print the call signature for any callable object.
%pdoc:
    Print the docstring for an object.
%pfile:
    Print (or run through pager) the file where an object is defined.
%pinfo:
    Provide detailed information about an object.
%pinfo2:
    Provide extra detailed information about an object.
%pip:
    Run the pip package manager within the current kernel.
%popd:
    Change to directory popped off the top of the stack.
%pprint:
    Toggle pretty printing on/off.
%precision:
    Set floating point precision for pretty printing.
%prun:
    Run a statement through the python code profiler.
%psearch:
    Search for object in namespaces by wildcard.
%psource:
    Print (or run through pager) the source code for an object.
%pushd:
    Place the current dir on stack and change directory.
%pwd:
    Return the current working directory path.
%pycat:
    Show a syntax-highlighted file through a pager.
%pylab:
    ::
%quickref:
    Show a quick reference sheet
%recall:
    Repeat a command, or get command to input line for editing.
%rehashx:
    Update the alias table with all executable files in $PATH.
%reload_ext:
    Reload an IPython extension by its module name.
%rep:
    Alias for `%recall`.
%rerun:
    Re-run previous input
%reset:
    Resets the namespace by removing all names defined by the user, if
%reset_selective:
    Resets the namespace by removing names defined by the user.
%rm:
    Alias for `!rm`
%rmdir:
    Alias for `!rmdir`
%run:
    Run the named file inside IPython as a program.
%save:
    Save a set of lines or a macro to a given filename.
%sc:
    Shell capture - run shell command and capture output (DEPRECATED use !).
%set_env:
    Set environment variables.  Assumptions are that either "val" is a
%store:
    Lightweight persistence for python variables.
%sx:
    Shell execute - run shell command and capture output (!! is short-hand).
%system:
    Shell execute - run shell command and capture output (!! is short-hand).
%tb:
    Print the last traceback.
%time:
    Time execution of a Python statement or expression.
%timeit:
    Time execution of a Python statement or expression
%unalias:
    Remove an alias
%unload_ext:
    Unload an IPython extension by its module name.
%who:
    Print all interactive variables, with some minimal formatting.
%who_ls:
    Return a sorted list of all interactive variables.
%whos:
    Like %who, but gives some extra information about each variable.
%xdel:
    Delete a variable, trying to clear it from anywhere that
%xmode:
    Switch modes for the exception handlers.
%%!:
    Shell execute - run shell command and capture output (!! is short-hand).
%%HTML:
    Alias for `%%html`.
%%SVG:
    Alias for `%%svg`.
%%bash:
    %%bash script magic
%%capture:
    ::
%%code_wrap:
    ::
%%debug:
    ::
%%file:
    Alias for `%%writefile`.
%%html:
    ::
%%javascript:
    Run the cell block of Javascript code
%%js:
    Run the cell block of Javascript code
%%latex:
    Render the cell as a block of LaTeX
%%markdown:
    Render the cell as Markdown text block
%%perl:
    %%perl script magic
%%prun:
    Run a statement through the python code profiler.
%%pypy:
    %%pypy script magic
%%python:
    %%python script magic
%%python2:
    %%python2 script magic
%%python3:
    %%python3 script magic
%%ruby:
    %%ruby script magic
%%script:
    ::
%%sh:
    %%sh script magic
%%svg:
    Render the cell as an SVG literal
%%sx:
    Shell execute - run shell command and capture output (!! is short-hand).
%%system:
    Shell execute - run shell command and capture output (!! is short-hand).
%%time:
    Time execution of a Python statement or expression.
%%timeit:
    Time execution of a Python statement or expression
%%writefile:
    ::

总结

  学习 Linux 的时候我就不太会记住那些命令，尤其是那些参数特别多的命令，所有经常会使用man、-h、--help、tab来查找文档和帮助拼写。IPython也是一样的，可以通过?、tab、%quickref来帮助我快速学习和完成拼写。当然，如果能全部记住就更好了。