trac代码阅读2 - yield expressions

例:

def test(value = None):

    i = value or 0

    while i < 100:

        yield i

        i += 1

=============>>>>>

>>> s.next()

0

>>> s.next()

1

>>> s.next()

2

>>> s.next()

3

由外部逻辑控制此generator function的执行,  we called it: Semi-Coroutine