Python multiprocessing pool, join; not waiting to go on?

Question

(1) I\'m trying to use pool.map followed by pool.join(), but python doesn\'t seem to be waiting for pool.map to finish before going on

Answer 1

This is not the correct way to use map.

1. Using a global variable that way is absolutely wrong. Processes do not share the same memory (normally) so every f will have his own copy of foo. To share a variable between different processes you should use a Manager
2. Function passed to map are, usually, expected to return a value.

I suggest you to read some documentation.

However here is a dummy example of how you could implement it:

from multiprocessing import Pool

foo = {1: []}

def f(x):
    return x

def main():
    pool = Pool()
    foo[1] = pool.map(f, range(100))
    pool.close()
    pool.join()
    print foo

if __name__ == '__main__':
    main()

You may also do something like pool.map(functools.partial(f, foo), range(100)) where foo is a Manager.