用yield单线程实现生产者，消费者模型.

async_exmaple.py

import time


def consumer():
    r = ''
    while True:
        n = yield r
        if not n:
            return
        print('[CONSUMER] Consuming %s...' % n)
        time.sleep(1)
        r = '200 OK'


def producer(c):
    next(c)
    for i in range(1, 10):
        print('[PRODUCER] Producing %s...' % i)
        r = c.send(i)
        print('[PRODUCER] Consumer return: %s ' % r)
    c.close()

if __name__ == '__main__':
    c = consumer()
    producer(c)