from sys import stdout
from multiprocessing import Process
from multiprocessing import Barrier

def task(barrier, number):

    for i in range(1, 400 + 1):
        print(f'{i}: {number}')
        barrier.wait()

if __name__ == '__main__':

    stdout.flush()
    num_workers = 500
    workers = list()

    # create a barrier
    barrier = Barrier(num_workers)

    # create the worker processes
    for i in range(1, num_workers + 1):
        workers.append(Process(target=task, args=(barrier, i)))
        workers[-1].start()

    # wait for all processes to finish
    for w in workers:
        w.join()