python中利用队列asyncio.Queue进行通讯详解

python中利用队列asyncio.Queue进行通讯详解

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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

总结

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