[Python-Dev] Cannot use multiprocessing and zip together on windows

Leo Jay python.leojay at gmail.com
Wed Dec 21 09:50:46 CET 2011

Hi All,

I posted this several days ago in python mailing list but got no response
and I think it might be a bug, so I post it here. Apologize if it's
not appropriate.

I have a file p.zip, there is a __main__.py in it, and the content of
__main__.py is:

from multiprocessing import Process
import os

def f():
  print 'in f, pid:', os.getpid()

if __name__ == '__main__':
  print 'pid:', os.getpid()
  p = Process(target=f)

On linux, I can get expected result for running "python p.zip"
But on windows xp, I got:

Traceback (most recent call last):
 File "<string>", line 1, in <module>
 File "C:\python27\lib\multiprocessing\forking.py", line 346, in main
 File "C:\python27\lib\multiprocessing\forking.py", line 454, in prepare
  assert main_name not in sys.modules, main_name
AssertionError: __main__

It seems that the situation described here is similar:

But the patch doesn't work for me.

Anybody knows how to fix this?

Best Regards,
Leo Jay

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