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Passing functions as parameter (multiprocessing)

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Fellows,

I'm having problems understanding an issue with passing function as parameters.

I'm sending some functions to the multiprocessing module (python 2.5 with the proper backport).
I'm iterating on a list of functions, however it seems that only the last function implementation is used for 
all the subprocesses.

Here's a code that triggers the issue:

 
import multiprocessing

def f1():
    print 'I am f1'
def f2(foo):
    print 'I am f2 %s' % foo

workers = [
        (f1,tuple()),
        (f2,(5,)),
        ]

procs=[]
for func, parameters in workers:
    # here it should be decorated, but for this example to be kept simple, the function is only wrapped, doing nothing special
    def subproc(*args, **kwargs):
        return func(*args, **kwargs)
    procs.append(multiprocessing.Process(target=subproc, args=parameters))

for proc in procs:
    proc.start()
for proc in procs:
    proc.join()


Here's the result:
> run test.py
Process Process-1:
Traceback (most recent call last):
  File "/usr/lib/python2.5/site-packages/multiprocessing-2.6.2.1-py2.5-linux-i686.egg/multiprocessing/process.py", line 237, in _bootstrap
    self.run()
  File "/usr/lib/python2.5/site-packages/multiprocessing-2.6.2.1-py2.5-linux-i686.egg/multiprocessing/process.py", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "test.py", line 17, in subproc
    return func(*args, **kwargs)
TypeError: f2() takes exactly 1 argument (0 given)
I am f2 5

It looks like the first subprocess is called with f2 instead of f1.

Any idea ?

JM


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Passing functions as parameter (multiprocessing) Jean-Michel Pichavant <jeanmichel@sequans.com> - 2012-11-13 13:19 +0100

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