无法腌制 python 中的 'weakref' 对象

Question

我正在尝试运行下面的代码，它的主要目的是做更复杂的程序，我用两个循环简化了它。

我不断收到以下错误：（我没有找到错误）

from multiprocessing import Process

def load():
    for i in range(0, 10000):
        print("loadddinngg", i)

def copy(p1):
    # fetch all files
    while p1.is_alive():
        for i in range(0, 100000):
            print("coppppyyy", i)

class multithreading:
    def __init__(self):
        p1 = Process(target=load, args=())

        p2 = Process(target=copy, args=( p1,))
        p1.start()
        p2.start()
        p1.join()
        p2.join()

 File "C:\Users\untitled10\toDelete.py", line 19, in __init__
    p2.start()
  File "C:\Program Files\Python38_64bit\lib\multiprocessing\process.py", line 121, in start
    self._popen = self._Popen(self)
  File "C:\Program Files\Python38_64bit\lib\multiprocessing\context.py", line 224, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
  File "C:\Program Files\Python38_64bit\lib\multiprocessing\context.py", line 327, in _Popen
    return Popen(process_obj)
  File "C:\Program Files\Python38_64bit\lib\multiprocessing\popen_spawn_win32.py", line 93, in __init__
    reduction.dump(process_obj, to_child)
  File "C:\Program Files\Python38_64bit\lib\multiprocessing\reduction.py", line 60, in dump
    ForkingPickler(file, protocol).dump(obj)
TypeError: cannot pickle 'weakref' object

Answer 1

进程对象的 args 被 pickle 以便将该信息发送到新进程（以便它可以在其自己的地址 Python 中解压并重新创建相同的 Python 对象=]).进程对象本身不能被 pickle。

另外，as stated in the documentation：

Note that the start(), join(), is_alive(), terminate() and exitcode methods should only be called by the process that created the process object.

因此我们不能指望在生成的进程中使用 is_alive。

要在进程之间进行通信，请使用 multiprocessing.Queue。对于这种特定情况，我们希望 p2 在 p1 完成后停止。这意味着，p1 必须告诉 p2 它即将完成，然后 p2 收到该消息并通过停止响应。

一个简单的例子可能如下所示：

from multiprocessing import Process, Queue
from queue import Empty # exception raised when the queue is empty
import sys

def load(q):
    do_some_work()
    # the actual object that we `put` in the Queue
    # doesn't matter for this trivial example.
    q.put(None) 

def copy(q):
    while True:
        do_some_other_work()
        try:
            q.get()
        except Empty:
            pass # the message wasn't sent yet.
        else:
            return # it was sent, so stop this thread too.

if __name__ == '__main__':
    q = Queue()
    p1 = Process(target=load, args=(q,))
    p2 = Process(target=copy, args=(q,))
    p1.start()
    p2.start()
    p1.join()
    p2.join()

无法腌制 python 中的 'weakref' 对象

cannot pickle 'weakref' object in python

python

multithreading