lesson04_barrier.py

# SuperFastPython.com
# example of using a barrier with processes
from time import sleep
from random import random
from multiprocessing import Process
from multiprocessing import Barrier

# custom function to be executed in a child process
def task(shared_barrier, ident):
    # generate a unique value between 0 and 10
    value = random() * 10
    # block for a moment
    sleep(value)
    # report result
    print(f'Process {ident} got: {value}', flush=True)
    # wait for all other processes to complete
    shared_barrier.wait()

# protect the entry point
if __name__ == '__main__':
    # create a barrier for (5 workers + 1 main process)
    barrier = Barrier(5 + 1)
    # create the worker processes
    workers = [Process(target=task,
        args=(barrier, i)) for i in range(5)]
    # start the worker processes
    for worker in workers:
        # start process
        worker.start()
    # wait for all worker processes to finish
    print('Main process waiting on all results...')
    barrier.wait()
    # report once all processes are done
    print('All processes have their result')