In this context it's worth noting that writing a memoizing decorator in Python is ridiculously easy:

  class memoized(object):
     def __init__(self, func):
        self.func = func
        self.cache = {}
     def __call__(self, *args):
        try:
           return self.cache[args]
        except KeyError:
           value = self.func(*args)
           self.cache[args] = value
           return value