threaded_fact.py

import threading
try:
    from Queue import Queue
except ImportError:
    from queue import Queue


def fact(n, queue=None):
    if n == 0 or n == 1:
        if queue:
            queue.put(1)
            return
        else:
            return 1
    q = Queue()
    t = threading.Thread(target=fact, args=(n - 1, q))
    t.start()
    result = q.get() * n
    if queue:
        queue.put(result)
        return
    else:
        return result

if __name__ == "__main__":
    import sys
    print (fact(int(sys.argv[1])))