fibonacci.py

def fib(n):
    a, b = 0, 1
    for _ in range(n):
        yield a
        a, b = b, a + b

k = fib(10)
>>> next(k)
0
>>> next(k)
1
>>> next(k)
1
>>> next(k)
2
>>> next(k)
3
>>> next(k)
5