python中利用队列asyncio.Queue进行通讯详解

前言

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asyncio.Queue与其它队列是一样的，都是先进先出，它是为协程定义的

例子如下：

import asyncio

async def consumer(n, q):
print('consumer {}: starting'.format(n))
while True:
 print('consumer {}: waiting for item'.format(n))
 item = await q.get()
 print('consumer {}: has item {}'.format(n, item))
 if item is None:
  # None is the signal to stop.
  q.task_done()
  break
 else:
  await asyncio.sleep(0.01 * item)
  q.task_done()
print('consumer {}: ending'.format(n))

async def producer(q, num_workers):
print('producer: starting')
# Add some numbers to the queue to simulate jobs
for i in range(num_workers * 3):
 await q.put(i)
 print('producer: added task {} to the queue'.format(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()

输出如下：

consumer 0: starting
consumer 0: waiting for item
consumer 1: starting
consumer 1: waiting for item
producer: starting
producer: added task 0 to the queue
producer: added task 1 to the queue
consumer 0: has item 0
consumer 1: has item 1
producer: added task 2 to the queue
producer: added task 3 to the queue
consumer 0: waiting for item
consumer 0: has item 2
producer: added task 4 to the queue
consumer 1: waiting for item
consumer 1: has item 3
producer: added task 5 to the queue
producer: adding stop signals to the queue
consumer 0: waiting for item
consumer 0: has item 4
consumer 1: waiting for item
consumer 1: has item 5
producer: waiting for queue to empty
consumer 0: waiting for item
consumer 0: has item None
consumer 0: ending
consumer 1: waiting for item
consumer 1: has item None
consumer 1: ending
producer: ending

来源：http://blog.csdn.net/caimouse/article/details/77916974