用生成器写斐波那契数列

def My_fib(n):
    a = 1
    b = 1
    i = 1
    while i <=n:
        if i <= 2:
            yield 1
        else:
            c = a + b #
            a = b
            b = c
            yield c
        i+=1
D = My_fib(3)
print(next(D))
print(next(D))
# for i in D:
#     print(i)