On Tue, Aug 24, 2010 at 4:51 AM, Steven D'Aprano email@example.com wrote:
But that's the thing... as far as I am concerned, a dynamically defined attribute *doesn't* exist. If it existed, __getattr__ would never be called. A minor semantic difference, to be sure, but it's real to me.
Eh? If "x.y" succeeds, in what sense does y not exist?
Whether I should care about the difference is a separate issue.
Right, you are breaking through too much abstraction.
Performance could be an issue, of course, if somebody writes an expensive __getattr__ or property. Computed attributes should be cheap.
Yes, and it should be considered the problem of the author of that property, not of the user.
But I'm actually more concerned about side-effects than performance.
Properties should not have side effects. That would be a problem when using them just as much as with hasattr().