memoize.py

# hash returns a string representation of a function's arguments
# so that we can use that as a key
def hash(args):
    return ":".join(map(str, args))

def memoize(fn):
    cache = {}
    def memoized_fn(*args):
        hashed = hash(args)
        if hashed in cache:
            return cache[hashed]
        ret = fn(*args)
        cache[hashed] = ret
        return cache[hashed]
    # Return wrapped function
    return memoized_fn

@memoize
def get_url_title(url):
    # Fake slow network connection
    time.sleep(1.5)
    return "Awesome title: %s" % url

@memoize
def recursive_fib(n):
    # 0 -> 0 and 1 -> 1
    if n < 2:
        return n
    return recursive_fib(n-1) + recursive_fib(n-2)

recursive_fib(200)