python yield实现协程(生产者-消费者)

def customer():
    r=""
    while True:
        n=yield r#，接收生产者的消息，并向消费者发送r
        print("customer receive",n)
        r="ok"

def produce(c):
    c.send(None)#第一次启动协程必须发送None值，否则报如下错误
    #TypeError: can‘t send non-None value to a just-started generator
    for i in range(6):
        print("start send to customer",i)
        r=c.send(i)#向消费者发送值
        print("receive customer",r)

c=customer()
produce(c)

start send to customer 0
customer receive 0
receive customer ok
start send to customer 1
customer receive 1
receive customer ok
start send to customer 2
customer receive 2
receive customer ok
start send to customer 3
customer receive 3
receive customer ok
start send to customer 4
customer receive 4
receive customer ok
start send to customer 5
customer receive 5
receive customer ok