A brief tour of the IPython notebook

Rendered by nbconvert using Reveal.js!

by Damián Avila

This document will give you a brief tour of the capabilities of the IPython notebook.
-You can view its contents by scrolling around, or execute each cell by typing Shift-Enter. -After you conclude this brief high-level tour, you should read the accompanying notebook -titled 01_notebook_introduction, which takes a more step-by-step approach to the features of the -system.
-The rest of the notebooks in this directory illustrate various other aspects and -capabilities of the IPython notebook; some of them may require additional libraries to be executed.

NOTE: This notebook must be run from its own directory, so you must cd -to this directory and then start the notebook, but do not use the --notebook-dir -option to run it from another location.

The first thing you need to know is that you are still controlling the same old IPython you're used to, -so things like shell aliases and magic commands still work:

In [1]:

pwd
-

- -

Out[1]:

u'/home/damian/Desarrollos/ipython_mtaui_slide'

In [2]:

ls
-

- -

COPYING.txt            IPython/     python-logo.svg  setupbase.py  setup.py*
-docs/                  ipython.py*  README.rst       setupegg.py*  tools/
-example_nb_tour.ipynb  MANIFEST.in  scripts/         setupext/     tox.ini
-

In [3]:

message = 'The IPython notebook is great!'
-# note: the echo command does not run on Windows, it's a unix command.
-!echo $message
-

- -

The IPython notebook is great!
-

- Plots with matplotlib -

IPython adds an 'inline' matplotlib backend, -which embeds any matplotlib figures into the notebook.

In [4]:

%pylab inline
-

- -

-Welcome to pylab, a matplotlib-based Python environment [backend: module://IPython.zmq.pylab.backend_inline].
-For more information, type 'help(pylab)'.
-

In [5]:

x = linspace(0, 3*pi, 500)
-plot(x, sin(x**2))
-title('A simple chirp');
-

- -

You can paste blocks of input with prompt markers, such as those from -the official Python tutorial

In [6]:

>>> the_world_is_flat = 1
->>> if the_world_is_flat:
-...     print "Be careful not to fall off!"
-

- -

Be careful not to fall off!
-

Errors are shown in informative ways:

In [7]:

%run non_existent_file
-

- -

ERROR: File `u'non_existent_file.py'` not found.
-

In [8]:

x = 1
-y = 4
-z = y/(1-x)
-

- -

---------------------------------------------------------------------------
-ZeroDivisionError                         Traceback (most recent call last)
-<ipython-input-8-dc39888fd1d2> in <module>()
-      1 x = 1
-      2 y = 4
-----> 3 z = y/(1-x)
-
-ZeroDivisionError: integer division or modulo by zero

When IPython needs to display additional information (such as providing details on an object via x? -it will automatically invoke a pager at the bottom of the screen:

In [9]:

magic
-

- -

Non-blocking output of kernel

If you execute the next cell, you will see the output arriving as it is generated, not all at the end.

In [10]:

import time, sys
-for i in range(8):
-    print i,
-    time.sleep(0.5)
-

- -

0 1 2 3 4 5 6 7
-

Clean crash and restart

We call the low-level system libc.time routine with the wrong argument via -ctypes to segfault the Python interpreter:

In [*]:

import sys
-from ctypes import CDLL
-# This will crash a Linux or Mac system; equivalent calls can be made on Windows
-dll = 'dylib' if sys.platform == 'darwin' else '.so.6'
-libc = CDLL("libc.%s" % dll) 
-libc.time(-1)  # BOOM!!
-

- -

Markdown cells can contain formatted text and code

You can italicize, boldface

build
lists

and embed code meant for illustration instead of execution in Python:

def f(x):
-    """a docstring"""
-    return x**2
-

or other languages:

if (i=0; i<n; i++) {
-  printf("hello %d\n", i);
-  x += 4;
-}
-

Courtesy of MathJax, you can include mathematical expressions both inline: -$e^{i\pi} + 1 = 0$ and displayed:

$$e^x=\sum_{i=0}^\infty \frac{1}{i!}x^i$$

Rich displays: include anyting a browser can show

Note that we have an actual protocol for this, see the display_protocol notebook for further details.

Images

An image can also be displayed from raw data or a url

In [12]:

Image(url='http://python.org/images/python-logo.gif')
-

- -

Out[12]:

SVG images are also supported out of the box (since modern browsers do a good job of rendering them):

In [13]:

from IPython.display import SVG
-SVG(filename='python-logo.svg')
-

- -

Out[13]:

- -

Embedded vs Non-embedded Images

As of IPython 0.13, images are embedded by default for compatibility with QtConsole, and the ability to still be displayed offline.

Let's look at the differences:

In [14]:

# by default Image data are embedded
-Embed      = Image(    'http://scienceview.berkeley.edu/view/images/newview.jpg')
-
-# if kwarg `url` is given, the embedding is assumed to be false
-SoftLinked = Image(url='http://scienceview.berkeley.edu/view/images/newview.jpg')
-
-# In each case, embed can be specified explicitly with the `embed` kwarg
-# ForceEmbed = Image(url='http://scienceview.berkeley.edu/view/images/newview.jpg', embed=True)
-

- -

In [15]:

Embed
-

- -

Out[15]:

In [16]:

SoftLinked
-

- -

Out[16]:

Video

And more exotic objects can also be displayed, as long as their representation supports -the IPython display protocol.

For example, videos hosted externally on YouTube are easy to load (and writing a similar wrapper for other -hosted content is trivial):

In [17]:

from IPython.display import YouTubeVideo
-# a talk about IPython at Sage Days at U. Washington, Seattle.
-# Video credit: William Stein.
-YouTubeVideo('1j_HxD4iLn8')
-

- -

Out[17]:

- - - -

Local Files

The above examples embed images and video from the notebook filesystem in the output -areas of code cells. It is also possible to request these files directly in markdown cells -if they reside in the notebook directory via relative urls prefixed with files/:

files/[subdirectory/]<filename>
-

For example, in the example notebook folder, we have the Python logo, addressed as:

<img src="files/python-logo.svg" />
-

External sites

You can even embed an entire page from another site in an iframe; for example this is today's Wikipedia -page for mobile users:

In [19]:

HTML('<iframe src=http://en.mobile.wikipedia.org/?useformat=mobile width=700 height=350></iframe>')
-

- -

Out[19]:

- -

Mathematics

And we also support the display of mathematical expressions typeset in LaTeX, which is rendered -in the browser thanks to the MathJax library.
-

Note that this is different from the above examples. Above we were typing mathematical expressions -in Markdown cells (along with normal text) and letting the browser render them; now we are displaying -the output of a Python computation as a LaTeX expression wrapped by the Math() object so the browser -renders it. The Math object will add the needed LaTeX delimiters ($$) if they are not provided:

In [20]:

from IPython.display import Math
-Math(r'F(k) = \int_{-\infty}^{\infty} f(x) e^{2\pi i k} dx')
-

- -

Out[20]:

-$$F(k) = \int_{-\infty}^{\infty} f(x) e^{2\pi i k} dx$$ -

With the Latex class, you have to include the delimiters yourself. This allows you to use other LaTeX modes such as eqnarray:

In [21]:

from IPython.display import Latex
-Latex(r"""\begin{eqnarray}
-\nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\
-\end{eqnarray}""")
-

- -

Out[21]:

-\begin{eqnarray} -\nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\ -\end{eqnarray} -

Or you can enter latex directly with the %%latex cell magic:

In [22]:

%%latex
-\begin{aligned}
-\nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\
-\end{aligned}
-

- -

-\begin{aligned} -\nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\ -\end{aligned} -

Loading external codes

Drag and drop a .py in the dashboard
Use %load with any local or remote url: the Matplotlib Gallery!

In this notebook we've kept the output saved so you can see the result, but you should run the next -cell yourself (with an active internet connection).

Let's make sure we have pylab again, in case we have restarted the kernel due to the crash demo above

In [23]:

%pylab inline
-

- -

-Welcome to pylab, a matplotlib-based Python environment [backend: module://IPython.zmq.pylab.backend_inline].
-For more information, type 'help(pylab)'.
-

In [24]:

%load http://matplotlib.sourceforge.net/mpl_examples/pylab_examples/integral_demo.py
-

- -

- IPython rocks! -

Just my little contribution... I have a lot of work to do but this is an exciting beginning!

You can check here for more information about this PR.

And you can find me at: