Using Pool map with a method of a class and a list

[Luca Cerone]

Hi guys,
I would like to apply the Pool.map method to a member of a class.

Here is a small example that shows what I would like to do:

from multiprocessing import Pool

class A(object):
   def __init__(self,x):
       self.value = x
   def fun(self,x):
       return self.value**x


l = range(10)

p = Pool(4)

op = p.map(A.fun,l)

#using this with the normal map doesn't cause any problem

This fails because it says that the methods can't be pickled.
(I assume it has something to do with the note in the documentation: "functionality within this package requires that the __main__ module be importable by the children.", which is obscure to me).

I would like to understand two things: why my code fails and when I can expect it to fail? what is a possible workaround?

Thanks a lot in advance to everybody for the help!

Cheers,
Luca