Python 3.5 多处理池和队列不起作用 [英] Python 3.5 multiprocessing pool and queue don't work

问题描述

我遇到了多处理问题.代码包含在下面.代码可以按预期执行，但是当取消注释self.queue = multiprocessing.Queue()时，该程序会立即退出，并且似乎无法成功启动子进程.

I encounter a multiprocessing problem. The code is included below. The code can execute as expected, but when uncommenting self.queue = multiprocessing.Queue(), this program will exit immediately and it seems that the subprocess can't be started successfully.

我不知道发生了什么.有人可以帮我吗?非常感谢！

I don't know what happened. Could someone help me out? Many Thanks!

import multiprocessing
import time

class Test:
    def __init__(self):
        self.pool = multiprocessing.Pool(1)
        #self.queue = multiprocessing.Queue()

    def subprocess(self):
        for i in range(10):
            print("Running")
            time.sleep(1)
        print("Subprocess Completed")

    def start(self):
        self.pool.apply_async(func=self.subprocess)
        print("Subprocess has been started")
        self.pool.close()
        self.pool.join()

    def __getstate__(self):
        self_dict = self.__dict__.copy()
        del self_dict['pool']
        return self_dict

    def __setstate__(self, state):
        self.__dict__.update(state)

if __name__ == '__main__':
    test = Test()
    test.start()

推荐答案

我可以重现你的问题，也没有 Traceback 提出.
这应该会引发以下错误，不知道为什么:

I can reproduce your Issue and also no Traceback raised up.
This should raise the following error, don't know why not:

运行时错误:队列对象只能通过继承在进程之间共享

将您的代码行替换为:

    m = multiprocessing.Manager()
    self.queue = m.Queue()  

为什么会发生这种情况?
multiprocessing.Queue 用于 one Process，您使用的是 multiprocessing.Pool，它使用多个 Process，你得用multiprocessing.Manager().Queue().

Why does this happens?
multiprocessing.Queue is for use with one Process, you are using multiprocessing.Pool, which uses multiple Process, you have to use multiprocessing.Manager().Queue().

使用 Python 测试:3.4.2

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