Python - 在 Windows 中的多进程下创建线程时出现“can't pickle thread.lock”错误

我陷入了我认为的基本多进程和线程问题。我已经设置了一个多进程，其中有一个线程。但是，当我在其中设置线程类时init函数，我收到以下错误：

“类型错误：无法pickle thread.lock对象”。

但是，如果线程是在线程之外设置的，则不会发生这种情况init功能。有谁知道为什么会发生这种情况？请注意，我使用的是 Windows。

下面的一些代码可以说明这个问题。如下所示，它运行良好。但是，如果从 DoStuff 内部调用 print_hello()initdef，那么就会出现错误，如果是在多进程的run() def中调用那就没问题了。

任何人都可以为我指出正确的方向，以便在调用时运行良好init？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)

看起来没有简单的答案，而且似乎是 Windows 的限制（在我的例子中是 Win 7、python 3.6）；在 Windows 上，您似乎需要先启动该进程，然后才能在拥有的对象内启动工作线程。

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

作为实验，我修改了您的代码如下；此版本检查操作系统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 上得到以下结果，其中进程首先启动：

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

...以及 Linux 上的以下内容，首先启动线程：

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

如果这是我的代码，我会倾向于先启动进程，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)