How can I recover the return value of a function passed to multiprocessing.Process?

Question

In the example code below, I\'d like to recover the return value of the function worker. How can I go about doing this? Where is this value stored?

Answer 1

I think the approach suggested by @sega_sai is the better one. But it really needs a code example, so here goes:

import multiprocessing
from os import getpid

def worker(procnum):
    print('I am number %d in process %d' % (procnum, getpid()))
    return getpid()

if __name__ == '__main__':
    pool = multiprocessing.Pool(processes = 3)
    print(pool.map(worker, range(5)))

Which will print the return values:

I am number 0 in process 19139
I am number 1 in process 19138
I am number 2 in process 19140
I am number 3 in process 19139
I am number 4 in process 19140
[19139, 19138, 19140, 19139, 19140]

If you are familiar with map (the Python 2 built-in) this should not be too challenging. Otherwise have a look at sega_Sai's link.

Note how little code is needed. (Also note how processes are re-used).