What is IPython?

Level 0: Interactive Python

def foo():
    """docstring"""
    return 'hi'
foo()

def bar():
    print 'hi'

from __future__ import print_function

import time

for i in range(10):
    time.sleep(0.25)
    print(i, end=' ')

import numpy as np

import ctypes
libc = ctypes.CDLL('libc.dylib')
libc.time(-1)

print("I'm okay!")

Level 1: A bit more than Python

import numpy as np

np.

np.linspace?

Shell interaction

!date

ls

files = !ls

for f in files:
    print(repr(f))

Extending Python with %magics

biglist = range(1000000)
bigset = set(biglist)

item = biglist[0]
%timeit item in biglist
%timeit item in bigset

def inner(x):
    return 1/x

def outer(y):
    return inner(1-y)

z = 2
outer(-z + 3)

%debug

%lsmagic

Level 2: A bit more than the Terminal

Rich Display

%matplotlib inline
import numpy as np
import matplotlib.pyplot as plt
from scipy.special import jn

x = np.linspace(0,10)
for n in range(5):
    plt.plot(x, jn(n,x))

%%latex
\begin{eqnarray}
\nabla \times \vec{\mathbf{B}} &
    - \frac{1}{c} \frac{\partial\vec{\mathbf{E}}}{\partial t} 
    & = & \frac{4 \pi}{c} \vec{\mathbf{j}} \\
\nabla \cdot \vec{\mathbf{E}} && = & 4 \pi \rho \\
\nabla \times \vec{\mathbf{E}} &
    + \frac{1}{c} \frac{\partial\vec{\mathbf{B}}}{\partial t}
    & = & \vec{\mathbf{0}} \\
\nabla \cdot \vec{\mathbf{B}} && = & 0 
\end{eqnarray}

import sympy
sympy.init_printing(use_latex='mathjax')
x = sympy.symbols('x')
expr = x**10-1
expr

sympy.factor(expr)

from IPython.display import display
from IPython.html.widgets import interact

@interact
def factorit(n=10):
    display(sympy.factor(x**n-1))
    

from IPython.display import Image, YouTubeVideo
Image("figs/darts.png")

YouTubeVideo('BROWqjuTM0g ')

Level 3: Documents

In the Notebook: not just code

We also have

• markdown and
• $\LaTeX$

var foo = $(".class");

What is a notebook?

name = "Background"
!head -n 100 {name}.ipynb | pygmentize -l json

!ipython nbconvert {name}.ipynb --to html

from IPython.display import display, HTML
display(HTML("<a href='{name}.html' target='_blank'>{name}.html</a>".format(name=name)))

But what is IPython, really?

A Protocol

Message type: execute_request

content = {
    # Source code to be executed by the kernel, one or more lines.
    'code' : str,

    # A boolean flag which, if True, signals the kernel to execute
    # this code as quietly as possible.
    'silent' : bool,

    # A boolean flag which, if True, signals the kernel to populate history
    # The default is True if silent is False.  If silent is True, store_history
    # is forced to be False.
    'store_history' : bool,
    ...
}

Message type: execute_reply

content = {
  # One of: 'ok' OR 'error'
  'status' : str,

  # The global kernel counter that increases by one with each request that
  # stores history.  This will typically be used by clients to display
  # prompt numbers to the user.  If the request did not store history, this will
  # be the current value of the counter in the kernel.
  'execution_count' : int,
}

Message type: display_data

content = {

    # The data dict contains key/value pairs, where the kids are MIME
    # types and the values are the raw data of the representation in that
    # format.
    'data' : dict,

    # Any metadata that describes the data
    'metadata' : dict,
}

%%javascript
IPython.notebook.kernel.execute("a=1");

print(a)

The protocol is publicly documented, and language agnostic.

So what is IPython, really?

• Tools for interactive computing
  • documents
  • interfaces
    • terminal
    • qtconsole
    • notebook
  • introspection
  • debugging
• A message protocol for remote execution
  • language-agnostic
  • rich remote repl

How does this become IPython.parallel?

Let's see a quick demo, and then find out in more detail.