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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