def fib(n):
if n == 0:
return 0
elif n == 1:
return 1
else:
return fib(n-1) + fib(n-2)
Calling the function:
>>> from fibonacci import fib
>>> fib(5)
5
>>> fib(0), fib(1), fib(2), fib(3)
(0, 1, 1, 2)