fibs.py

#!/usr/bin/env python

"""A few different (but really the same) ways to create the Fibonacci sequence."""

from pprint import pprint as pp

def fibs1():
    '''Generate the Fibonacci sequence.'''
    x, y = 0, 1
    while True:
        x, y = x + y, x
        yield x

def fibs2():
    '''Generate the Fibonacci sequence using a mutable default arg.'''
    def _fib(x=[0, 1]):
        x.reverse()
        x[0] = sum(x)
        return x[0]
    while True:
        yield _fib()

def fibs3():
    '''Generate the Fibonacci sequence by flipping a list.'''
    x = [0, 1]
    while True:
        x.reverse()
        x[0] = sum(x)
        yield x[0]

d, e, f = fibs1(), fibs2(), fibs3()

pp([next(d) for i in range(12)])
pp([next(e) for i in range(12)])
pp([next(f) for i in range(12)])