进程中join方法的使用

在进程中：join方法 是让主进程等待子进程运行完毕后再执行主进程的。（即主进程阻塞）

示例

# -*- coding: utf-8 -*-
from multiprocessing import Process
import time

class MyProcess(Process):
    def __init__(self, name, n):
        super().__init__()
        self.name = name
        self.n = n

    def run(self):
        print('进程%s is running，%s' % (self.n, self.name))
        time.sleep(self.n)
        print('进程%s is done %s' % (self.n, self.name))

if __name__ == '__main__':
    p_ls = []
    start_time = time.time()
    for i in range(1,5):
        p = MyProcess('qzk', i)
        p_ls.append(p)
        p.start()
    for p in p_ls:
        p.join()
    print(' 主进程执行', time.time() - start_time)

# 进程1 is running，qzk
# 进程4 is running，qzk
# 进程2 is running，qzk
# 进程3 is running，qzk
# 进程1 is done qzk
# 进程2 is done qzk
# 进程3 is done qzk
# 进程4 is done qzk
#  主进程执行 4.15123724937439