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')