Python

Question

我被困在我认为是基本的多进程和线程问题上。我已经设置了一个多进程，并且在这个线程中。但是，当我在 init 函数中设置线程 class 时，出现以下错误：

"TypeError: can't pickle thread.lock objects".

但是，如果在 init 函数之外设置线程，则不会发生这种情况。有谁知道为什么会这样？注意我正在使用 Windows.

下面是一些代码来说明这个问题。如下所示，它运行没问题。但是，如果从 DoStuff init def 中调用 print_hello()，则会发生错误，如果在多进程运行() def 中调用，则没关系。

任何人都可以指出正确的方向，以便从 init 调用时运行没问题吗？谢谢！

import multiprocessing
import threading
import time

class MyProcess(multiprocessing.Process):

    def __init__(self, **kwargs):
        super(MyProcess, self).__init__(**kwargs)
        self.dostuff = DoStuff()

    def run(self):
        print("starting DoStuff")
        # This works fine if the line below is uncommented and __init__ self.print_hello() is commented...
        self.dostuff.print_hello()


class DoStuff(object):
    def __init__(self, **kwargs):
        super(DoStuff, self).__init__(**kwargs)

        # If the following is uncommented, the error occurs...
        #   Note it also occurs if the lines in start_thead are pasted here...
        # self.print_hello()

    def print_hello(self):
        print "hello"
        self.start_thread()

    def start_thread(self):
        self.my_thread_instance = MyThread()
        self.my_thread_instance.start()
        time.sleep(0.1)


class MyThread(threading.Thread):
    def __init__(self):
        super(MyThread, self).__init__()

    def run(self):
        print("Starting MyThread")


if __name__ == '__main__':
    mp_target = MyProcess()       # Also pass the pipe to transfer data
    # mp_target.daemon = True
    mp_target.start()
    time.sleep(0.1)

Answer 1

看起来没有简单的答案，似乎是Windows的限制（我的情况是Win 7，python 3.6）；在 Windows 上，您似乎需要先启动进程，然后才能在拥有的对象中启动工作线程。

Unix (CentOS 7, python 2.7.5) 似乎没有这样的限制。

作为实验，我修改了您的代码如下；此版本检查 OS 并首先启动进程，或首先启动线程：

import multiprocessing
import threading
import time
import os

class MyProcess(multiprocessing.Process):

    def __init__(self, **kwargs):
        super(MyProcess, self).__init__(**kwargs)
        self.dostuff = DoStuff(self)

    def run(self):
        print("MyProcess.run()")
        print("MyProcess.ident = " + repr(self.ident))
        if os.name == 'nt':
            self.dostuff.start_thread()

class DoStuff(object):
    def __init__(self, owner, **kwargs):
        super(DoStuff, self).__init__(**kwargs)
        self.owner = owner
        if os.name != 'nt':
            self.start_thread()

    def start_thread(self):
        print("DoStuff.start_thread()")
        self.my_thread_instance = MyThread(self)
        self.my_thread_instance.start()
        time.sleep(0.1)

class MyThread(threading.Thread):
    def __init__(self, owner):
        super(MyThread, self).__init__()
        self.owner = owner

    def run(self):
        print("MyThread.run()")
        print("MyThread.ident = " + repr(self.ident))
        print("MyThread.owner.owner.ident = " + repr(self.owner.owner.ident))

if __name__ == '__main__':
    mp_target = MyProcess()       # Also pass the pipe to transfer data
    mp_target.daemon = True
    mp_target.start()
    time.sleep(0.1)

... 并在 Windows 上获得以下信息，其中进程首先开始：

MyProcess.run()
MyProcess.ident = 14700
DoStuff.start_thread()
MyThread.run() 
MyThread.ident = 14220
MyThread.owner.owner.ident = 14700

...以及 Linux 上的以下线程首先启动的位置：

DoStuff.start_thread()
MyThread.run()
MyThread.ident = 140316342347520
MyThread.owner.owner.ident = None
MyProcess.run()
MyProcess.ident = 4358

如果是我的代码，我会很想总是先启动进程，然后在该进程中创建线程；以下版本在两个平台上都适合我：

import multiprocessing
import threading
import time

class MyProcess(multiprocessing.Process):

    def __init__(self, **kwargs):
        super(MyProcess, self).__init__(**kwargs)
        self.dostuff = DoStuff()

    def run(self):
        print("MyProcess.run()")
        self.dostuff.start_thread()

class DoStuff(object):
    def __init__(self, **kwargs):
        super(DoStuff, self).__init__(**kwargs)

    def start_thread(self):
        self.my_thread_instance = MyThread()
        self.my_thread_instance.start()
        time.sleep(0.1)

class MyThread(threading.Thread):
    def __init__(self):
        super(MyThread, self).__init__()

    def run(self):
        print("MyThread.run()")

if __name__ == '__main__':
    mp_target = MyProcess()       # Also pass the pipe to transfer data
    mp_target.daemon = True
    mp_target.start()
    time.sleep(0.1)

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