memoize.py

def memoize(f):
    computed = {}
    def memoized(*args):
        xs = computed.get(args)
        if xs : 
            return xs
        else : 
            value = f(*args)
            computed[args] = value
            return value
    return memoized


def fact(n):
    print("computing", n)
    if n == 0:
        return 1
    else:
        return fact(n-1) * n