Fibonachi Number

fib.py

def cache(fn):
    _cached = {}
    def wrap(*args, **kwargs):
        key = repr((args, kwargs))
        if key not in _cached:
            value = fn(*args, **kwargs)
            _cached[key] = value
        return _cached[key]
    return wrap

@cache
def fib(n):
    if n <= 0:
        return 0
    elif n == 1:
        return 1
    return fib(n-1) + fib(n-2)


import unittest

class TestFib(unittest.TestCase):
    def test_fib(self):
        self.assertEqual(fib(250), 7896325826131730509282738943634332893686268675876375)

if __name__ == '__main__':
    unittest.main()