python基础-面向对象（十八）面向对象进阶（六）迭代器协议实现斐波那契数列

a = 2
b = 5
print(b)
a, b = b, a + b
print(b)
a, b = b, a + b
print(b)

class Test:
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def __iter__(self):
        return self

    def __next__(self):
        if self.b > 20:
            raise StopIteration
        self.a, self.b = self.b, self.a + self.b
        return self.b


test = Test(0, 1)
for i in test:  # for 循环就是在执行__next__
    print(i)

def shulie(a, b, max):
    while b < max:
        a, b = b, a + b
        yield b  # yield执行一次会退出并挂起。下次从挂起的地方继续


for i in shulie(0, 1, 20):  # for 循环就是在执行__next__
    print(i)