En Thu, 30 Apr 2009 17:59:55 -0300, Jared Grubb escribió:

The only thing I dislike is how many dictionary lookups are required in order to return the value after it's been cached. I count 4 lookups (object.prop, prop.__call__, self._cache, and self._cache[args]). These add up, especially if object.prop could have returned the value immediately without having to go through so much indirection (but this is not currently possible)

It is not possible if one insist on using property. But Oleg Broytmann's CachedAttribute class works fine -- it seems to me it didn't get the deserved attention. I'll repost a slightly modified version: class CachedAttribute(object): def __init__(self, method, name=None): self.method = method self.name = name or method.__name__ self.__doc__ = method.__doc__ def __get__(self, inst, cls): if inst is None: return self result = self.method(inst) setattr(inst, self.name, result) return result class Foo(object): @CachedAttribute def expensive(self): "docstring for the expensive property" print("computing value...") return 42 py> f = Foo() py> f.expensive computing value... 42 py> f.expensive 42 py> f.expensive = 43 py> f.expensive 43 py> del f.expensive py> f.expensive computing value... 42 py> f.expensive 42 py> Note that once the value is computed, it becomes an instance attribute; later accesses retrieve it directly, no indirection is involved. -- Gabriel Genellina Yahoo! Cocina Recetas prácticas y comida saludable http://ar.mujer.yahoo.com/cocina/