如何将队列字典传递给 multiprocessing.Process

Question

我不确定是否可以将队列字典作为参数传递给进程。如果只能作为kwargs，那怎么办？

from multiprocessing import Process, Queue


class WordsManager:

    def __init__(self, my_dict):
        self.dict = my_dict

    def run(self):
        pass


def words_worker(my_dict):
    worker = WordsManager(my_dict)
    worker.run()


def start_job_manager():
    my_dict = {}
    for language in ('en', 'de', 'es'):
        my_dict[language] = Queue()

    words_manager = {'process': None, 'my_dict': my_dict}
    words_manager["process"] = Process(target=words_worker, args=(words_manager['my_dict']))
    words_manager["process"].daemon = True
    words_manager["process"].start()

    return words_manager


start_job_manager()

错误是：

Process Process-4:
Traceback (most recent call last):
   File "/home/antonio/python/lib/python3.4/multiprocessing/process.py", line 254, in _bootstrap
self.run()
  File "/home/antonio/python/lib/python3.4/multiprocessing/process.py", line 93, in run
self._target(*self._args, **self._kwargs)
TypeError: words_worker() takes 1 positional argument but 3 were given

Answer 1

如果我在元素后使用逗号，它会正常运行

args=(words_manager['my_dict'],)

我想如果没有逗号，Python 会将字典中的每个值解释为一个参数，但是如果有逗号，它会被视为一个包含 words_manager['my_dict'] 的元组作为唯一的论点。

Answer 2

问题出在您传递给进程的参数中：

args=(words_manager['my_dict'])

大括号不会被解释为元组，因此您不会将一系列参数传递给 args。相反，您应该通过在末尾放置 , 来显式创建一个 1 元素元组：

args=(words_manager['my_dict'],)

来自Python Docs：

A special problem is the construction of tuples containing 0 or 1 items: the syntax has some extra quirks to accommodate these. Empty tuples are constructed by an empty pair of parentheses; a tuple with one item is constructed by following a value with a comma (it is not sufficient to enclose a single value in parentheses). Ugly, but effective.

如何将队列字典传递给 multiprocessing.Process

How to pass a dictionary of Queues to multiprocessing.Process

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python-multiprocessing