import multiprocessing as mp
import time

def func(a,_,b):
    return a + b

def this_works(pool, queue):
    w = []
    for i in range(10):
        w.append(pool.apply_async(func, args=(i, queue, i + 2), callback=lambda x: print(x)))
    while any([x for x in w if not x.ready()]):
        time.sleep(0.1)

def and_this_is_broken(pool, queue):
    w = []
    for i in range(10):
        w.append(pool.apply_async(func, args=(i, queue, i + 100), callback=lambda x: print(x)))
    while any([x for x in w if not x.ready()]):
        time.sleep(0.1)

if __name__ == '__main__':
    pool = mp.Pool(processes=2)

    queue = mp.Manager().Queue()
    this_works(pool, queue)

    queue = mp.Queue()
    and_this_is_broken(pool, queue)