等待一个子进程

使用场景：父进程在某个阶段等待子进程

# join方法
from multiprocessing import Process
import time, os
def task():
    print('%s is running,parent id is <%s>' % (os.getpid(), os.getppid()))
    time.sleep(3)
    print('%s is done,parent id is <%s>' % (os.getpid(), os.getppid()))
if __name__ == '__main__':
    p = Process(target=task, )
    p.start()
    p.join()
    print('主', os.getpid(), os.getppid())
    print(p.pid)

等待多个子进程

from multiprocessing import Process
import time, os
def task(name, n):
    print('%s is running' % name)
    time.sleep(n)
if __name__ == '__main__':
    start = time.time()
    p1 = Process(target=task, args=('子进程1', 5))
    p2 = Process(target=task, args=('子进程2', 3))
    p3 = Process(target=task, args=('子进程3', 2))
    p_l = [p1, p2, p3]
    for p in p_l:
        p.start()
    for p in p_l:
        p.join()
    print('主', (time.time() - start))