Groups > comp.lang.python > #52059

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

Newsgroups	comp.lang.python
Date	2013-08-06 10:12 -0700
Message-ID	<96c575da-7601-4023-aa91-e80664f90333@googlegroups.com> (permalink)
Subject	Using Pool map with a method of a class and a list
From	Luca Cerone <luca.cerone@gmail.com>

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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

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Thread

Using Pool map with a method of a class and a list Luca Cerone <luca.cerone@gmail.com> - 2013-08-06 10:12 -0700
  Re: Using Pool map with a method of a class and a list Chris Angelico <rosuav@gmail.com> - 2013-08-06 18:38 +0100
    Re: Using Pool map with a method of a class and a list Luca Cerone <luca.cerone@gmail.com> - 2013-08-06 12:42 -0700
      Re: Using Pool map with a method of a class and a list Joshua Landau <joshua@landau.ws> - 2013-08-07 07:48 +0100
        Re: Using Pool map with a method of a class and a list Luca Cerone <luca.cerone@gmail.com> - 2013-08-07 01:33 -0700
          Re: Using Pool map with a method of a class and a list Joshua Landau <joshua@landau.ws> - 2013-08-07 10:47 +0100
            Re: Using Pool map with a method of a class and a list Luca Cerone <luca.cerone@gmail.com> - 2013-08-07 03:10 -0700
              Re: Using Pool map with a method of a class and a list Joshua Landau <joshua@landau.ws> - 2013-08-07 12:53 +0100
                Re: Using Pool map with a method of a class and a list Luca Cerone <luca.cerone@gmail.com> - 2013-08-07 15:26 -0700
                Re: Using Pool map with a method of a class and a list Joshua Landau <joshua@landau.ws> - 2013-08-07 23:49 +0100
              Re: Using Pool map with a method of a class and a list Peter Otten <__peter__@web.de> - 2013-08-07 16:46 +0200
              Re: Using Pool map with a method of a class and a list Joshua Landau <joshua@landau.ws> - 2013-08-07 16:52 +0100
              Re: Using Pool map with a method of a class and a list Peter Otten <__peter__@web.de> - 2013-08-07 18:15 +0200
                Re: Using Pool map with a method of a class and a list Luca Cerone <luca.cerone@gmail.com> - 2013-08-07 16:31 -0700
  Re: Using Pool map with a method of a class and a list Luca Cerone <luca.cerone@gmail.com> - 2013-08-06 12:37 -0700

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