Compilation of ipython features or tricks I use to help developing/exploring

ipython_tricks.md

Ipython tricks

Here I'll describe some ipython tricks to make developing or exploring bugs easier.

First: What is ipython? It's an interactive Python terminal with colours, autocompletion and some additional magic.

Install it with: sudo pip install --upgrade ipython

Autocompletion

Just press TAB to autocomplete almost anything, imports, functions, methods...

This is very useful to interactively understand the state of some object. Note that you can also use dir(my_object) to find out all the methods/fields it has.

Check docs

Just add ? to any function/method and you'll get the help.

Get the result of the last line executed

It's always in the _ variable, just write _ or print(_).

Time a function/method

Just use the magic method %timeit like, %timeit my_method().

Move into directories, get autocompletion on file choosing

You can use some commands as if you were in the shell normally, like cd, ls...

Save the output of a shell command into a variable (SUPER EASY AND USEFUL)

Just write your command with an exclamation mark ! in front (and save it), like output = ! ps aux | grep ipython.

This is superuseful for one-off tasks that are easy to solve in python partially and easy to solve partially in bash.

Check your history of commands and save it

Access the history by doing %history and save it (as explained here) with %save:

In [15]: %save -r mysession 1-99999
The following commands were written to file `mysession.ipy`:

Use an ipython shell as a debugging breakpoint

You can add to your script the line: import ipdb; ipdb.set_trace()

And you will be dropped into an ipython shell with all the autocompletion capabilities to explore the state of your program.

Note that you may need to install:

sudo apt-get install libncurses5-dev
sudo pip install --upgrade ipdb ipython readline

Others

Docs are here: https://ipython.readthedocs.io/en/stable/interactive/magics.html

I haven't used them much but there are interesting ones like %run that runs a program in the ipython shell, and then you get all the variables to explore interactively.

You can also define alias for commands.

You can also use matplotlib inside of ipython: https://matplotlib.org/stable/users/interactive.html