Prototype of an extension to provide acess to virtual python environment on an IPython notebook cell

test_virtualenvmagic.py

# -*- coding: utf-8 -*-

import os
import nose.tools as nt
from IPython.core.interactiveshell import InteractiveShell

def setup():
    ip = InteractiveShell()
    ip.extension_manager.load_extension('virtualenvmagic')
    
def test_virtualenv():
    ip = InteractiveShell()
    result = ip.run_cell_magic('virtualenv','my_env','import sys; print sys.version')
    nt.assert_true(result.startswith('2.7.3'))
    
    
    

virtualenvmagic.py

"""
Virtualenv magic
Requires virtualenv and virtualenv Wrapper
"""
import sys
import os
import shlex
from subprocess import Popen, PIPE
from IPython.core.magic import cell_magic
from IPython.core.interactiveshell import InteractiveShell

@cell_magic('virtualenv')
def virtualenv(line, cell):
    """
    This magic enables the excution of the code of the cell on a 
    pre-existing virtualenv.
    
    Usage
    =====
    
    To activate this magic just write at the top of the cell:
    %% virtualenv my_env
    """
    if not os.path.exists(os.environ['WORKON_HOME']+line):
        print >> sys.stderr, "Environment {} does no exist.".format(line)
        return
    env_activate_cmd = 'bash -c source '+os.environ['WORKON_HOME'] + '/{}/bin/activate'.format(line)
    cmd = shlex.split(env_activate_cmd) + ["&&","python","-"]
    p = Popen(cmd, stdout=PIPE, stderr=PIPE, stdin=PIPE, shell=True)
    out,err = p.communicate(cell)
    if err:
        print >> sys.stderr, err
    return out

if 'WORKON_HOME' in os.environ:
    #~ get_ipython().register_magic_function(virtualenv, 'cell')
    InteractiveShell().register_magic_function(virtualenv, 'cell')

@minrk : Would this be a start of a virtualenv cell?

it requires virtualenv to be installed and the env to exist prior to using this

Rather than calling get_ipython() or InteractiveShell(), an IPython extension should offer a load_ipython_extension(ip) method, which will be called with the shell object when it's loaded. Docs: http://ipython.org/ipython-doc/stable/config/extensions/index.html

(The rationale for this is that we have a long term goal to allow more than one InteractiveShell object in the same process - so we're trying not to treat it like a singleton)

I'll study other extensions and modify my code to conform.
thanks @takluyver

Thanks @turicas for the tip on how to make the bash command work...

@fccoelho, PEP8, please! :-)