更新multiprocessing.Manager.dict（）中的对象

Question

我想知道如何更新在不同进程之间分配为共享字典值的对象。我有以下课程：

class Task:

    STATUS_PROCESSING = 0
    STATUS_EXECUTING = 1
    STATUS_QUEUED = 2
    STATUS_TERMINATED = 3
    STATUS_HALTED = 4
    STATUS_STOPPED = 5

    def __init__(self, id: str, uuid: str, options: dict):
        self.id = id
        self.uuid = uuid
        self.options = options
        self.state = 0

    # Some properties...

    def execute(self):
        """ Executes the task
        """
        # Set self status to Executing
        self.state = Task.STATUS_EXECUTING

        print('Executing...')

        self.state = Task.STATUS_TERMINATED

它仅创建具有给定ID的新任务，并在调用execute()时执行其核心方法。我还有另一个带有静态方法的类，该类用于将新对（id，任务）添加到字典，并读取执行所有任务的字典，直到主程序停止：

class DummyList:

    @staticmethod
    def submit_task(d: dict, uuid: str, options: dict):
        """ Submit a new task
        """
        # If invalid UUID
        if not Task.is_valid_uuid(uuid):
            return False

        # If more than 20 tasks
        if len(d) > 19:
            return False

        # Create random ID (simplified for question)
        r_id = str(random.randint(1, 2000000))
        if r_id in d:
            return False

        # Add task to the dictionary
        d[r_id] = Task(r_id, uuid, options)

        # Set status to queue
        d[r_id].state = Task.STATUS_QUEUED

        # Return the created ID
        return r_id

    @staticmethod
    def execute_forever(d):
        try:
            while True:
                for i in d.values():
                    print(i.state)
                    i.execute()
                time.sleep(5)
        except KeyboardInterrupt:
            pass

事实是DummyList.execute_forever()将从另一个进程中调用，而主进程将执行submit_task(...)函数以添加新任务。像这样：

        # Create a shared dict
        m = multiprocessing.Manager()
        shared_d = m.dict()

        # Start the Task shared list execution in another process
        p = multiprocessing.Process(target=DummyList.execute_forever, args=(shared_d,))
        # Set the process to exit when the main halts
        p.daemon = True
        p.start()

        ........


       # From another place
       # The message variable is not important
       DummyList.submit_task(shared_d, message['proc'], message['options'])

有效！该任务已创建，分配给字典并执行，但是以下几行（在上面的代码中可见）无法正确执行：

self.state = Task.STATUS_EXECUTING
self.state = Task.STATUS_TERMINATED
d[r_id].state = Task.STATUS_QUEUED

如果我们尝试在整个代码中编写ìf shared_d[<some_id>].state == 0，则它将始终为True，因为该属性不会更新

我想这是因为共享字典在修改对象属性时不会更新，可能是因为字典仅了解他必须在调用getitem或setitem方法时更新。你知道有什么办法可以改变这种行为吗？

非常感谢！

Answer 1

我终于找到了解决方案。除非调用代理字典中的__getitem__或__setitem__方法，否则字典中的对象不会更新。这就是为什么我更改了以下几行：

任务

execute()方法以return self结尾。在整个执行过程中，必须更改self.state。

TaskManager

方法更改为：

@staticmethod
    def execute_forever(d):
        """ Infinite loop reading the queued tasks and executing all of them.
        """
        try:
            while True:
                # Notice the loop using the keys
                for i in d.keys():
                    # Execute and re-assign item
                    d[i] = d[i].execute()
                time.sleep(5)
        except KeyboardInterrupt:
            pass