Fibonacci sequence with a generator

fibgen.py

def fib(n):
    a, b = 1, 0
    while a < n:
        yield a
        a, b = b, a+b


# example:
'''
The 'yield' key word allows this function to be iterable.
Doesn't build up a list in memory, returns the 'next' one along.
'''
for n in fib(100):
    print n