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PODumping a multiprocessing.Queue into a list
 

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    <p>I wish to dump a <code>multiprocessing.Queue</code> into a list. For that task I've written the following function:</p> <pre><code>import Queue def dump_queue(queue): """ Empties all pending items in a queue and returns them in a list. """ result = [] # START DEBUG CODE initial_size = queue.qsize() print("Queue has %s items initially." % initial_size) # END DEBUG CODE while True: try: thing = queue.get(block=False) result.append(thing) except Queue.Empty: # START DEBUG CODE current_size = queue.qsize() total_size = current_size + len(result) print("Dumping complete:") if current_size == initial_size: print("No items were added to the queue.") else: print("%s items were added to the queue." % \ (total_size - initial_size)) print("Extracted %s items from the queue, queue has %s items \ left" % (len(result), current_size)) # END DEBUG CODE return result </code></pre> <p>But for some reason it doesn't work.</p> <p>Observe the following shell session:</p> <pre><code>&gt;&gt;&gt; import multiprocessing &gt;&gt;&gt; q = multiprocessing.Queue() &gt;&gt;&gt; for i in range(100): ... q.put([range(200) for j in range(100)]) ... &gt;&gt;&gt; q.qsize() 100 &gt;&gt;&gt; l=dump_queue(q) Queue has 100 items initially. Dumping complete: 0 items were added to the queue. Extracted 1 items from the queue, queue has 99 items left &gt;&gt;&gt; l=dump_queue(q) Queue has 99 items initially. Dumping complete: 0 items were added to the queue. Extracted 3 items from the queue, queue has 96 items left &gt;&gt;&gt; l=dump_queue(q) Queue has 96 items initially. Dumping complete: 0 items were added to the queue. Extracted 1 items from the queue, queue has 95 items left &gt;&gt;&gt; </code></pre> <p>What's happening here? Why aren't all the items being dumped?</p>
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