Am I misunderstanding the Python documentation?

Although not absolutely necessary, I thought it would be nice to have a multiprocessing Queue that I could use in the style of a Work Manager.

This is what I wrote:

from multiprocessing import Queue

class WMQueue(Queue):
    def __init__(self):
        super().__init__()
    def __enter__(self):
        return self
    def __exit__(self, *_):
        self.close()

This induces the following exception:

TypeError: method expected 2 arguments, got 3

The reason is that multiprocessing.Queue is a method.

However, the documentation for Queue is as follows:

class multiprocessing.Queue([maxsize])

In fact, the Queue method returns an object of type multiprocessing.queues.Queue which, as I can't find any documentation for it, is probably unsafe to [try to] subclass.

I know how I can re-write my class so that it could be used as WM but that's not the point. If Queue was a class, as documented, then I should be able to simply subclass it.

Or am I misunderstanding Python documentation?

If you want to inherit from something, inherit from multiprocessing.queues.Queue.

You're correct in that the documentation isn't entirely correct, since multiprocessing.Queue is indeed an alias for the multiprocessing.context._default_context.Queue factory that is defined over here and does

    def Queue(self, maxsize=0):
        from .queues import Queue
        return Queue(maxsize, ctx=self.get_context())

As an aside, if all you want to do is call close() on a queue at context manager exit time, use contextlib.closing:

q = Queue()
with contextlib.closing(q):
   # ...

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