Minimal Cython implementation (modeled from training.enthought.com example)

cyfib.pyx

def cyfib(int n):
    cdef int a, b, i
    a,b = 1,1
    for i in range(n):
        a,b = a+b, a
    return a

fib.py

import pyximport
pyximport.install()
from cyfib import cyfib

def fib(n):
    a,b = 1,1
    for i in range(n):
        a,b = a+b, a
    return a

print fib(5)
print cyfib(5)