Make IPython work with multiprocessing

[ipython]

Original Launchpad bug 315251: https://bugs.launchpad.net/ipython/+bug/315251
Reported by: gael-varoquaux (Gael Varoquaux).

Because the '.module' attribute of functions defined interactively in IPython is set to a virtual module non existant on the disk, distributing these functions with multiprocessing does not work:

resting ~ $ ipython
Python 2.5.2 (r252:60911, Jul 31 2008, 17:28:52) 
Type "copyright", "credits" or "license" for more information.

IPython 0.9.1 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object'. ?object also works, ?? prints more.

In [1]: import multiprocessing as mp

In [2]: p = mp.Pool(2)

In [3]: def foo(x):
   ...:     return 2*x
   ...: 

In [4]: p.map(foo, range(4))
Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/lib/python2.5/threading.py", line 486, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.5/threading.py", line 446, in run
    self.__target(*self.__args, **self.__kwargs)
  File "build/bdist.linux-i686/egg/multiprocessing/pool.py", line 225, in _handle_tasks
PicklingError: Can't pickle : attribute lookup __builtin__.function failed

[fperez]

Darren Dale also provided this example that shows what I believe is the same problem. We need to ensure that both do work before closing the ticket.

from multiprocessing import Pool

import IPython.core.ipapi as ip
ip.get()

def update(i):
   print i

def f(i):
   return i*i

if __name__ == '__main__':
   pool = Pool()
   for i in range(10):
       pool.apply_async(f, [i], callback=update)
   pool.close()
   pool.join()

Upon running Darren's, I see this:

dreamweaver[test]> python darren_bug.py 
Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/lib/python2.6/threading.py", line 532, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.6/threading.py", line 484, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/usr/lib/python2.6/multiprocessing/pool.py", line 225, in _handle_tasks
    put(task)
PicklingError: Can't pickle : attribute lookup __builtin__.function failed

[minrk]

This is the same bug as #29

[minrk]

Closing to merge with #29