Communication between processes using Queue

A simple way to communicate between process with multiprocessing is to use a Queue to pass messages back and forth. Any Python object can pass through a Queue.

import multiprocessing


def square_list(mylist: list, q: multiprocessing.Queue):
    """
    function to square a given list
    """
    # append squares of mylist to queue
    for num in mylist:
        q.put(num * num)


def print_queue(q: multiprocessing.Queue):
    """
    function to print queue elements
    """
    print("Queue elements:")
    while not q.empty():
        print(q.get())
    print("Queue is now empty!")


if __name__ == "__main__":
    # input list
    mylist = [1, 2, 3, 4]

    # creating multiprocessing Queue
    q = multiprocessing.Queue()

    # creating new processes
    p1 = multiprocessing.Process(target=square_list, args=(mylist, q))
    p2 = multiprocessing.Process(target=print_queue, args=(q,))

    # running process p1 to square list
    p1.start()
    p1.join()

    # running process p2 to get queue elements
    p2.start()
    p2.join()

References
https://www.geeksforgeeks.org/multiprocessing-python-set-2/

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