python resettable instance method memoization decorator

Question

I\'m attempting to build a decorator for an instance method of a class that will memoize the result. (This has been done a million times before) However, I\'d like the optio

Answer 1

Well, I would like to point out two performance issues in your code. This is not an answer to your question, but I can't make it a comment. Thanks to @delnan for pointing out that has_key is deprecated. Instead of:

    try:
        return self.cache[key]
    except KeyError:
        self.cache[key] = self.func(*args, **kwargs)
        return self.cache[key]
    except TypeError:
        # uncacheable, so just return calculated value without caching
        return self.func(*args, **kwargs)

I would make it this way:

resultDone = False
result = None
try:
  if key in self.cache: return self.cache[key]
  else:
    result = self.func(*args, **kwargs)
    resultDone = True
    self.cache[key] = result
except TypeError: # unhashable key
  pass
if resultDone: return result
else: return self.func(*args, **kwargs)

This avoids: a) try/except KeyError; b) calling cache[key] on return; c) calling the function once more on unhashable keys.