day29-1 守护进程

叁歲伎倆 2021-12-01 23:42 509阅读 0赞

# 守护进程 #

**守护进程会在主进程代码执行结束后和主进程一起终止**

# 守护进程
    import time
    from multiprocessing import Process
    
    
    def task1():
        print('son1 process run:', time.ctime())
        time.sleep(3)
        print('son1 process stop:', time.ctime())
    
    
    def task2():
        print('son2 process run:', time.ctime())
        time.sleep(5)
        print('son2 process stop:', time.ctime())
    
    
    if __name__ == '__main__':
        p1 = Process(target=task1)
        p2 = Process(target=task2)
    
        p1.daemon = True  # 将p1子进程设为主进程的守护进程，必须要写在开启该子进程的前面
        p1.start()  # 开启进程p1
        p2.start()  # 开启进程p2
    
        time.sleep(1)
        print('parent process stop:', time.ctime())
    -----------------------------------------------------------------
    son2 process run: Wed Jul  3 15:34:43 2019  
    son1 process run: Wed Jul  3 15:34:43 2019
    parent process stop: Wed Jul  3 15:34:44 2019  # 在子进程结束时，p1子进程跟着结束，所以son1 process stop不打印
    son2 process stop: Wed Jul  3 15:34:48 2019

**守护进程内无法再开启子进程，否则抛出异常：AssertionError: daemonic processes are not allowed to have children**

# 在守护进程内开启子进程，抛出异常：AssertionError: daemonic processes are not allowed to have children
    import time
    from multiprocessing import Process
    
    
    def task11():
        print('son son process:', time.ctime())
    
     
    def task1():
        p11 = Process(target=task11)
        p11.start()
    
    
    if __name__ == '__main__':
        p1 = Process(target=task1)
    
        p1.daemon = True
        p1.start()
    
        time.sleep(1)
        print('parent process stop:', time.ctime())
    -----------------------------------------------------------------------------
    Process Process-1:
    Traceback (most recent call last):
      File "C:\Python3\lib\multiprocessing\process.py", line 258, in _bootstrap
        self.run()
      File "C:\Python3\lib\multiprocessing\process.py", line 93, in run
        self._target(*self._args, **self._kwargs)
      File "E:\python9\day32\test.py", line 16, in task1
        p11.start()
      File "C:\Python3\lib\multiprocessing\process.py", line 103, in start
        'daemonic processes are not allowed to have children'
    AssertionError: daemonic processes are not allowed to have children
    parent process stop: Wed Jul  3 15:42:33 2019

# 不设守护进程，在子进程内开启子进程.类似于一种嵌套
    import time
    from multiprocessing import Process
    
    
    def task11():
        print('son1 son process:', time.ctime())
    
    
    def task1():
        p11 = Process(target=task11)
        p11.start()
        time.sleep(1)
        print('son process:',time.ctime())
    
    
    if __name__ == '__main__':
        p1 = Process(target=task1)
        p1.start()
        time.sleep(1)
        print('parent process stop:', time.ctime())
    -----------------------------------------------------------------------------
    son1 son process: Wed Jul  3 15:48:34 2019
    parent process stop: Wed Jul  3 15:48:34 2019
    son process: Wed Jul  3 15:48:35 2019

转载于:https://www.cnblogs.com/863652104kai/p/11126964.html