Configuring IPython

Finding configuration options

IPython has many configuration attributes. These can be viewed using the -h flag to the command line applications:

In []:
!ipython -h

This is an important trick for finding out configuration info:

$> ipython [subcommand] --help-all | grep [-C context] PATTERN

--help-all exposes everything configurable in IPython, there is a good chance you will find what you are looking for.

A common configuration question is:

how do I disable the "Do you really want to exit" message when quitting with Ctrl-d?

Well, logically this has to do with exit, so let's look for it:

In []:
!ipython --help-all | grep exit

Which shows me that I can disable the confirmation for a single IPython session with

$> ipython --no-confirm-exit

or I can set the TerminalInteractiveShell.confirm_exit=False in a config file, to have it be the default behavior.

Configuration principles

Here are the design principles of the IPython configuration system:

The IPython Profile

IPython has a notion of 'profiles' - these are directories that live in your IPYTHONDIR, which contain configuration and runtime information.

Let's create the default profile

In []:
!ipython profile create

This creates a profile in your IPYTHONDIR (ipython locate is a quick way to see where your IPYTHONDIR is), and populates it with automatically generated default config files.

In []:
!ipython locate profile default

You can skim

In []:
profile = get_ipython().profile_dir.location
profile
In []:
ls $profile

Let's peek at our config file

In []:
pycat $profile/ipython_config.py

The %config magic

The %config magic lets you do some configuration at runtime, rather than in configuration files.

In []:
%pylab inline

%config with no arguments will show you what configurable objects exist:

In []:
%config

And %config Class will show you the config for that class:

In []:
%config InlineBackend

Most importantly, the %config magic can be used to change the value of a configurable attribute at runtime. Here we tell the inline matplotlib backend to use SVG instead of the default PNG

In []:
x = linspace(0,10,1000)
y = sin(x)
plot(x,sin(x))
In []:
%config InlineBackend.figure_format = 'svg'
In []:
plot(x,sin(x))

Defining your own magic

As we have seen already, IPython has cell and line magics. You can define your own magics using any Python function and the register_magic_function method:

In []:
ip = get_ipython()
In []:
def sleep_magic(line):
    """A simple function for sleeping"""
    t = float(line)
    import time
    time.sleep(t)
In []:
ip.register_magic_function(sleep_magic, "line", "sleep")
In []:
%sleep 2
In []:
%sleep?
In []:
ip.magics_manager.define_magic?

Exercise

Define %tic and %toc magics, which can be use for simple timings, e.g. where

for p in range(1,4):
    N = 10**p
    print "N=%i" % N
    %tic
    A = np.random.random((N,N))
    np.linalg.eigvals(A)
    %toc

each %toc will print the time since the last %tic. Create separate tic and toc functions that read and write a global time variable.

In []:
%load soln/tictocf.py
In []:
import time

def format_time(dt):
    if dt < 1e-6:
        return u"%.3g ns" % (dt * 1e9)
    elif dt < 1e-3:
        return u"%.3g ┬Ás" % (dt * 1e6)
    elif dt < 1:
        return u"%.3g ms" % (dt * 1e3)
    else:
        return "%.3g s" % dt

def tic(line):
    global t0
    t0 = time.time()

def toc(line):
    global t0
    print format_time(time.time() - t0)

ip = get_ipython()
ip.register_magic_function(tic)
ip.register_magic_function(toc)
In []:
import numpy as np

for p in range(1,4):
    N = 10**p
    print "N=%i" % N
    %tic
    A = np.random.random((N,N))
    np.linalg.eigvals(A)
    %toc

Startup files

Startup files are simple Python or IPython scripts that are run whenever you start IPython. These are a useful way to do super common imports, or for building database connections to load on startup of a non-default profile.

We can use a startup file to ensure that our %tic/toc magics are always defined, every time we start IPython.

In []:
!ls $profile/startup

Adding common imports, so we never have to forget them again

In []:
%%file simpleimports.py

import sys, os, time, re
In []:
!cp simpleimports.py $profile/startup/simpleimports.py

And the same can be done for our tic/toc magics

In []:
!cp soln/tictocf.py $profile/startup/tictocf.py

Restart the kernel and then run the following cells immediately to verify these scripts have been executed:

In []:
sys
In []:
%tic
time.sleep(0.5)
%toc

Orignal Source: IPython: Interactive Computing in Python's Git repository