Python3标准库：asyncio异步I/O、事件循环和并发工具(8)

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Python3标准库：asyncio异步I/O、事件循环和并发工具(8)

(i))
			# Add None entries in the queue

			# to signal the consumers to exit

			print('producer: adding stop signals to the queue')

			for i in range(num_workers):

			await q.put(None)

			print('producer: waiting for queue to empty')

			await q.join()

			print('producer: ending')

			async def main(loop, num_consumers):

			# Create the queue with a fixed size so the producer

			# will block until the consumers pull some items out.

			q = asyncio.Queue(maxsize=num_consumers)

			# Scheduled the consumer tasks.

			consumers = [

			loop.create_task(consumer(i, q))

			for i in range(num_consumers)

			]

			# Schedule the producer task.

			prod = loop.create_task(producer(q, num_consumers))

			# Wait for all of the coroutines to finish.

			await asyncio.wait(consumers + [prod])

			event_loop = asyncio.get_event_loop()

			try:

			event_loop.run_until_complete(main(event_loop, 2))

			finally:

			event_loop.close()

用put()增加元素和用get()删除元素都是异步操作，因为队列大小可能是固定的（阻塞增加操作），或者队列可能为空（阻塞获取元素的调用）。

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