問題描述

import multiprocessing
import time

class testM(multiprocessing.Process):

    def __init__(self):
        multiprocessing.Process.__init__(self)
        self.exit = False

    def run(self):
        while not self.exit:
            pass
        print "You exited!"
        return

    def shutdown(self):
        self.exit = True
        print "SHUTDOWN initiated"

    def dostuff(self):
        print "haha", self.exit


a = testM()
a.start()
time.sleep(3)
a.shutdown()
time.sleep(3)
print a.is_alive()
a.dostuff()
exit()

我只是想知道為什么上面的代碼并沒有真正打印你退出".我究竟做錯了什么?如果是這樣，有人可以指出正確退出的正確方法嗎?(我不是指 process.terminate 或 kill)

I am just wondering how come the code above doesn't really print "you exited". What am I doing wrong? if so, may someone point me out the correct way to exit gracefully? (I am not referring to process.terminate or kill)

推薦答案

您沒有看到這種情況發生的原因是因為您沒有與子進程通信.您正在嘗試使用局部變量(父進程的本地變量)向子進程發出它應該關閉的信號.

The reason you are not seeing this happen is because you are not communicating with the subprocess. You are trying to use a local variable (local to the parent process) to signal to the child that it should shutdown.

查看有關同步原語的信息.您需要設置可以在兩個進程中引用的某種信號.一旦你有了這個，你應該能夠在父進程中輕按開關并等待子進程死亡.

Take a look at the information on synchonization primatives. You need to setup a signal of some sort that can be referenced in both processes. Once you have this you should be able to flick the switch in the parent process and wait for the child to die.

試試下面的代碼:

import multiprocessing
import time

class MyProcess(multiprocessing.Process):

    def __init__(self, ):
        multiprocessing.Process.__init__(self)
        self.exit = multiprocessing.Event()

    def run(self):
        while not self.exit.is_set():
            pass
        print "You exited!"

    def shutdown(self):
        print "Shutdown initiated"
        self.exit.set()


if __name__ == "__main__":
    process = MyProcess()
    process.start()
    print "Waiting for a while"
    time.sleep(3)
    process.shutdown()
    time.sleep(3)
    print "Child process state: %d" % process.is_alive()

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