Passing functions as parameter (multiprocessing)
Jean-Michel Pichavant
jeanmichel at sequans.com
Tue Nov 13 07:19:15 EST 2012
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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