from multiprocessing import Pool

def power (x, pwr=2):
    return x**pwr

import functools
run_test = functools.partial (power, pwr=3)

if __name__ == "__main__":

    pool = Pool()
    cases = [3,4,5]
    results = pool.map (run_test, cases)

TypeError: type 'partial' takes at least one argument
Traceback (most recent call last):
  File "/usr/lib/python2.5/site-packages/multiprocessing-2.6.1.1-py2.5-
    self.run()
  File "/usr/lib/python2.5/site-packages/multiprocessing-2.6.1.1-py2.5-
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python2.5/site-packages/multiprocessing-2.6.1.1-py2.5-
    task = get()
  File "/usr/lib/python2.5/site-packages/multiprocessing-2.6.1.1-py2.5-
    return recv()
TypeError: type 'partial' takes at least one argument

See this mail thread:
http://mail.python.org/pipermail/python-dev/2009-February/086034.html

Rather than implement a multiprocessing-specific fix, it would certainly
be better to make functools.partial picklable, as pointed out in the ML
thread Jesse linked to.

> Antoine Pitrou <pitrou@free.fr> added the comment:
>
> Rather than implement a multiprocessing-specific fix, it would certainly
> be better to make functools.partial picklable, as pointed out in the ML
> thread Jesse linked to.
>

I would tend to agree

I agree that this is a nice feature, however it requires adding a 
getstate/setstate within the functools C code. 

I would need a patch which does this, and adds tests to the 
functools/pickle test suite for this. Also, the feature will only be 
accepted for py3k (3.1) currently. Features such as this will not be 
backported to the 2.x branch

Jack offered to take a peek

Fixed rev 70931.  Happy pickling!