类型错误：无法pickle 'weakref' 对象

Question

这里的多处理相当新。我有一个运行两个进程的代码。一种是不断地从服务器接收数据块并将其放入队列中，另一种是从队列中取出数据块并对其进行处理。

下面是我的客户端代码：

import socket
import turtle
import multiprocessing
from multiprocessing import Process, Queue
from tkinter import *


class GUI:

    def __init__(self, master):
        rec_data = recv_data()
        self.master = master
        master.title("Collision Detection")

        self.input_label = Label(root, text="Input all the gratings set straight wavelength values in nm")
        self.input_label.grid(row=0)

        self.core_string = "Core "
        self.entries = []


        self.label_col_inc = 0
        self.entry_col_inc = 1
        self.core_range = range(1, 5)

        for y in self.core_range:
            self.core_text = self.core_string + str(y) + '_' + '25'
            self.core_label = Label(root, text=self.core_text)
            self.entry = Entry(root)
            self.core_label.grid(row=1, column=self.label_col_inc, sticky=E)
            self.entry.grid(row=1, column=self.entry_col_inc)
            self.entries.append(self.entry)
            self.label_col_inc += 2
            self.entry_col_inc += 2

        self.threshold_label = Label(root, text="Threshold in nm")
        self.entry_threshold = Entry(root)

        self.threshold_label.grid(row=2, sticky=E)
        self.entry_threshold.grid(row=2, column=1)

        self.light_label = Label(root, text='Status')
        self.light_label.grid(row=3, column=3)

        self.canvas = Canvas(root, width=150, height=50)
        self.canvas.grid(row=4, column=3)

        # Green light
        self.green_light = turtle.RawTurtle(self.canvas)
        self.green_light.shape('circle')
        self.green_light.color('grey')
        self.green_light.penup()
        self.green_light.goto(0, 0)

        # Red light
        self.red_light = turtle.RawTurtle(self.canvas)
        self.red_light.shape('circle')
        self.red_light.color('grey')
        self.red_light.penup()
        self.red_light.goto(40, 0)

        self.data_button = Button(root, text="Get data above threshold", command=rec_data.getData)
        self.data_button.grid(row=5, column=0)


class recv_data:
    def __init__(self):
        self.buff_data = multiprocessing.Queue()
        self.p1 = multiprocessing.Process(target=self.recvData)
        self.p2 = multiprocessing.Process(target=self.calculate_threshold)
        self.host = '127.0.0.1'
        self.port = 5001
        self.s = socket.socket()
        self.s.connect((self.host, self.port))

    # function to receive TCP data blocks
    def getData(self):
        len_message = self.s.recv(4)
        bytes_length = int(len_message.decode('utf-8'))  # for the self-made server
        recvd_data = self.s.recv(bytes_length)
        self.buff_data.put(recvd_data)
        self.p1.start()
        self.p2.start()

        self.p1.join()
        self.p2.join()

    def recvData(self):
        len_message = self.s.recv(4)
        while len_message:
            bytes_length = int(len_message.decode('utf-8'))  # for the self-made server
            recvd_data = self.s.recv(bytes_length)
            self.buff_data.put(recvd_data)
            len_message = self.s.recv(4)

        else:
            print('out of loop')
        self.s.close()

    def calculate_threshold(self):
        rmv_data = self.buff_data.get()
        stringdata = rmv_data.decode('utf-8')
        rep_str = stringdata.replace(",", ".")
        splitstr = rep_str.split()

        # received wavelength values
        inc = 34
        wav_threshold = []
        for y in gui.entries:
            straight_wav = float(y.get())
            wav = float(splitstr[inc])
            wav_diff = wav - straight_wav
            if wav_diff < 0:
                wav_diff = wav_diff * (-1)
            wav_threshold.append(wav_diff)
            inc += 56

        threshold = float(gui.entry_threshold.get())

        for x in wav_threshold:
            if (x > threshold):
                gui.red_light.color('red')
                gui.green_light.color('grey')

            else:
                gui.red_light.color('grey')
                gui.green_light.color('green')
    

        # function to write into the file

    def write_file(self, data):
        with open("Output.txt", "a") as text_file:
            text_file.write('\t'.join(data[0:]))
            text_file.write('\n')

if __name__ == '__main__':
    root = Tk()
    gui1 = GUI(root)

    root.mainloop()

我得到的错误如下所示：

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Users\AppData\Local\Programs\Python\Python38-32\lib\tkinter\__init__.py", line 1883, in __call__
    return self.func(*args)
  File "C:/Users/PycharmProjects/GUI/GUI_multiprocess.py", line 85, in getData
    self.p2.start()
  File "C:\Users\AppData\Local\Programs\Python\Python38-32\lib\multiprocessing\process.py", line 121, in start
    self._popen = self._Popen(self)
  File "C:\Users\AppData\Local\Programs\Python\Python38-32\lib\multiprocessing\context.py", line 224, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
  File "C:\Users\AppData\Local\Programs\Python\Python38-32\lib\multiprocessing\context.py", line 326, in _Popen
    return Popen(process_obj)
  File "C:\Users\AppData\Local\Programs\Python\Python38-32\lib\multiprocessing\popen_spawn_win32.py", line 93, in __init__
    reduction.dump(process_obj, to_child)
  File "C:\Users\AppData\Local\Programs\Python\Python38-32\lib\multiprocessing\reduction.py", line 60, in dump
    ForkingPickler(file, protocol).dump(obj)
TypeError: cannot pickle 'weakref' object
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "C:\Users\AppData\Local\Programs\Python\Python38-32\lib\multiprocessing\spawn.py", line 116, in spawn_main
    exitcode = _main(fd, parent_sentinel)
  File "C:\Users\AppData\Local\Programs\Python\Python38-32\lib\multiprocessing\spawn.py", line 126, in _main
    self = reduction.pickle.load(from_parent)
EOFError: Ran out of input

我在这里做错了什么，我该如何解决？任何帮助表示赞赏。谢谢！

Answer 1

我刚刚遇到了相同的回溯并设法解决了它。这是因为一个对象有一个正在运行或退出的进程作为变量，并且它正在使用该对象启动另一个进程。

问题

这是产生错误的最小代码：

import multiprocessing

class Foo:
    def __init__(self):
        self.process_1 = multiprocessing.Process(target=self.do_stuff1)
        self.process_2 = multiprocessing.Process(target=self.do_stuff2)

    def do_multiprocessing(self):
        self.process_1.start()
        self.process_2.start()

    def do_stuff1(self):
        print("Doing 1")

    def do_stuff2(self):
        print("Doing 2")

if __name__ == '__main__':
    foo = Foo()
    foo.do_multiprocessing()

[out]:
Traceback (most recent call last):
  File "myfile.py", line 21, in <module>
    foo.do_multiprocessing()
  File "myfile.py", line 11, in do_multiprocessing
    self.process_2.start()
  File "...\lib\multiprocessing\process.py", line 121, in start
    self._popen = self._Popen(self)
  File "...\lib\multiprocessing\context.py", line 224, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
  File "...\lib\multiprocessing\context.py", line 327, in _Popen
    return Popen(process_obj)
  File "...\lib\multiprocessing\popen_spawn_win32.py", line 93, in __init__
    reduction.dump(process_obj, to_child)
  File "...\lib\multiprocessing\reduction.py", line 60, in dump
    ForkingPickler(file, protocol).dump(obj)
TypeError: cannot pickle 'weakref' object
Doing 1
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "...\lib\multiprocessing\spawn.py", line 116, in spawn_main
    exitcode = _main(fd, parent_sentinel)
  File "...\lib\multiprocessing\spawn.py", line 126, in _main
    self = reduction.pickle.load(from_parent)
EOFError: Ran out of input

所以，问题是，富也包含运行/退出过程foo.process_1当它开始foo.process_2。

解决方案1

将foo.process_1设置为 None 或其他。或者将 Processes 存储在foo以外的其他地方，以防止在启动process_2时被传递。

...
def do_multiprocessing(self):
    self.process_1.start()
    self.process_1 = None # Remove exited process
    self.process_2.start()
...

解决方案2

从酸洗中删除有问题的变量（process_1）：

class Foo:
    def __getstate__(self):
        # capture what is normally pickled
        state = self.__dict__.copy()

        # remove unpicklable/problematic variables 
        state['process_1'] = None
        return state
...

这在较新的 Python 版本中似乎是个问题。我自己的代码在 3.7 上运行良好，但由于 3.9 中的这个问题而失败。

我测试了你的代码（来自recv_data）。由于您加入进程并需要它们，因此您应该执行解决方案 2 或将进程存储在recv_data以外的其他位置。不确定您的代码还有哪些其他问题。