Generator和Coroutine学习

 简单的生产者消费者模型

#!/usr/bin/python2.7

def consumer():
    while True:
        newn = yield
        print 'Consumer : {}'.format(newn)

def producer(func):
    func.next()       # 必须实例化，否则：TypeError: can't send non-None value to a just-started generator
    # func.send(None)   等价于 func.next()
    n = 0
    while n < 5:
        print 'Producer : {}'.format(n)
        func.send(n)
        n += 1
    func.close()

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

# 结果如下：
Producer : 0
Consumer : 0
Producer : 1
Consumer : 1
Producer : 2
Consumer : 2
Producer : 3
Consumer : 3
Producer : 4
Consumer : 4

yield表达式示例

#!/usr/bin/python2.7

def count_down(n=5):
    while n > 0:
        newn = yield n
        if newn:
            n = newn
        else:
            n -= 1

if __name__ == '__main__':
    c = count_down()
    for num in c:
        print num
        if 5 == num:
            c.send(3)
            # tmp = c.send(3) 此时tmp就是 3 

# 结果如下:
5
2
1