Every once in a while I want to run a program in parallel but gather its output in a single process so that I do not have concurrent accesses (think for example, several process computing something and storing the output in a file or in a database). I could use locks for this but I figure I could also use a queue.

My problem is that I always forget how I do it and always need to search for it when I want to do it again :-) So for you as much as for me here is an example:

# -*- coding: utf-8 -*-

import itertools
from multiprocessing import Pool, Manager

def do_something(arg):
    """ This function does something important in parallel but where we
    want to centralize the output, thus using the queue
    data, myq = arg
    print data

data = range(100)
m = Manager()
q = m.Queue()
p = Pool(5)
p.map(do_something, itertools.product(data, [q]))

with open('output', 'w') as stream:
    while q.qsize():
        print q.qsize()
        item = q.get()
        print item
        stream.write('%s\n' % item)

There are probably other/better ways to do this but that's a start :-)