alternative.py

def memoize(fn):
  cache = dict()
  
  def closure(*args):
    if args not in cache:
      cache[args] = fn(*args)
    return cache[args]
    
  return closure

memoize.py

def memoize(f):
    class memodict(dict):
        def __getitem__(self, *key):
            return dict.__getitem__(self, key)

        def __missing__(self, key):
            ret = self[key] = f(*key)
            return ret

    return memodict().__getitem__
    
@memoize
def foo(a, b):
    return a * b