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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?
612
Passing Keyword Arguments to Multiprocessing Processes We can also pass in arguments corresponding to the parameter name using the kwargs parameter in the Process class. Instead of passing a tuple, we pass a dictionary to kwargs where we specify the argument name and the variable being passed in as that argument.
apply_async() The apply_async() function can be called directly to execute a target function in the process pool. The call will not block, but will instead immediately return an AsyncResult object that we can ignore if our function does not return a value.
Pass the keyword args in a dictionary (and the positional arguments in a tuple):
pool.apply_async(test, (t,), dict(arg2=5))
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})
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