show me the code

def fab(max): 
    n, a, b = 0, 0, 1 
    while n < max: 
        yield b 
        # print b 
        a, b = b, a + b 
        n = n + 1 
        ...


>>> for n in fab(5): 
...     print n 
... 
1 
1 
2 
3 
5

yield一般用在用循環(huán)功能的函數(shù)內(nèi)，用在把循環(huán)里的數(shù)據(jù)提取出來(lái)，有點(diǎn)像OC的block