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

workon_magic.py

import sys
import os
import shlex
from subprocess import Popen, PIPE
from IPython.utils.py3compat import unicode_to_str

def workon(line, cell):
    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
    print out

if 'WORKON_HOME' in os.environ:
    get_ipython().register_magic_function(workon, 'cell')

"""
From now, you can do:

%%workon pre_existing_env
# Now the following python code will be executed under pre_existing_env
import sys
print sys.version

"""

@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! :-)