multiprocessing Queue subclass issue

Question

I want to subclass multiprocessing.Queue for implementing processes to grab chunks of the queue. The only problem is, I'm getting a weird TypeError?

#!/usr/bin/env python

#whaaaaa!?

from multiprocessing import Queue

class BufferQueue(Queue):
    '''A thread/process safe queue for append/popleft operations with the import
    buffer.'''

    def __init__(self, **kwargs):
        super(BufferQueue,self).__init__(**kwargs)

    def consume(self, lim):
        '''Consume up to but no more than lim elements and return them in a new
        list, cleaning up the buffer.

        @params
        lim -- the maximum (limit) to consume from the list.  If less items
        exist in the list then that's fine too.
        '''
        lim = len(queue) if len(queue) < lim else lim
        return [self.popleft() for i in range(lim)]

testing this (I split this out so that I wasn't pulling in anything else)

| => ./tests/wtf_queue.py 
Traceback (most recent call last):
  File "./tests/wtf_queue.py", line 10, in <module>
    class BufferQueue(Queue):
TypeError: method expected 2 arguments, got 3

Edit/Update:

Answer 1

multiprocessing.Queue is a method that creates queues, so you're supposed to use it as a function my_queue = Queue().

>>> from multiprocessing import Queue
>>> type(Queue)
<class 'method'>

As you can see is not a 'type', which you would use to subclass.

If you want to implement your own queue, you could take a look at queue.Queue

EDIT:

If you want to subclass the queue from multiprocessing, use multiprocessing.queues.Queue instead, which is the type of the object returned by multiprocessing.Queue()