how do I use key word arguments with python multiprocessing pool apply_async
Solution 1
Pass the keyword args in a dictionary (and the positional arguments in a tuple):
pool.apply_async(test, (t,), dict(arg2=5))
Solution 2
original answer: python multiprocessing with boolean and multiple arguments
apply_async has args and kwds keyword arguments which you could use like this:
res = p.apply_async(testFunc, args=(2, 4), kwds={'calcY': False})
Solution 3
Janne's answer didn't work for me in python 2.7.11 (not sure why). The function test() was receiving the key (arg2), not the value (5).
I fixed this by creating a wrapper around test:
def test2(argsDict):
test(**argsDict)
Then calling
pool.apply_async(test2, (t,), [dict(arg2=5)])
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cts
Updated on June 05, 2022Comments
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cts almost 2 years
I'm trying to get to grips with pythons multiprocessing module, specifically the apply_async method of
Pool
. I'm trying to call a function with arguments and keyword arguments. If I call the function without kwargs it's fine but when I try to add in a keyword argument I get:TypeError: apply_async() got an unexpected keyword argument 'arg2'
Below is the test code that I'm running#!/usr/bin/env python import multiprocessing from time import sleep def test(arg1, arg2=1, arg3=2): sleep(5) if __name__ == '__main__': pool = multiprocessing.Pool() for t in range(1000): pool.apply_async(test, t, arg2=5) pool.close() pool.join()
How can I call the function so that it accepts keyword arguments?
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Ravindranath Akila about 7 yearsThe thing is, if it is a wrapper, we don't need keyword arguments :) I too confirm the issue of test receiving the key