On Thu, 15 Nov 2012 15:46:19 -0700, Ian Kelly wrote: > Although you don't go into it in the blog entry, what I like about your > approach of replacing the descriptor with an attribute is that, in > addition to being faster, it makes it easy to force the object to lazily > reevaluate the attribute, just by deleting it.
You just lost me right there. That's a poor UI design -- it violates the principle of least surprise. If I delete something, it should be deleted. Consider your example: >>>> del p.display_name >>>> p.display_name > 'Eliza Smith' That's very surprising. I am not aware of any other name in Python where deleting it does not remove the name from the namespace. (It is possible with properties, but I haven't ever come across someone who does that.) I don't have a good solution for invaliding such lazy attributes. Ideally we could have a new statement: refresh obj.attr # or some other name like "invalidate" but that won't happen. Other alternatives like: obj.attr.refresh() refresh(obj.attr) can't work because the function will see the result of the attribute lookup, not the lazy attribute itself. This won't do: obj.__class__.attr.refresh() because it won't know which instance to invalidate, although this could work: obj.__class__.attr.refresh(obj) # but it's ugly I'm very vaguely leaning towards this as the least-worst solution to invalidating the cached value: refresh(obj, 'attr') # pass the instance and the name -- Steven -- http://mail.python.org/mailman/listinfo/python-list
