python進程與線程

同一個進程內，多個線程共享全局變量

import threading

n = 100


def start():
    global n
    n = 0


if __name__ == '__main__':
    t = threading.Thread(target=start())
    t.start()
    t.join()
    print('main process', n)  # output: main 0

多個進程間不共享變量

import multiprocessing

n = 100


def start():
    global n
    n = 0


if __name__ == '__main__':
    p = multiprocessing.Process(target=start)
    p.start()
    p.join()
    print('main', n)  # output: main 100