fib.py

from itertools import islice, imap, tee  
from operator import add    

def tail(iterable):
  return islice(iterable, 1, None)

def take(n, iterable):
  return list(islice(iterable, 0, n))

def fibs():
  yield 1
  yield 1
  fibs1, fibs2 = tee(fibs())
  yield from map(add, fibs1, tail(fibs2))