Op 2005-11-03, Steven D'Aprano schreef <[EMAIL PROTECTED]>: > On Thu, 03 Nov 2005 14:13:13 +0000, Antoon Pardon wrote: > >> Fine, we have the code: >> >> b.a += 2 >> >> We found the class variable, because there is no instance variable, >> then why is the class variable not incremented by two now? > > Because b.a += 2 expands to b.a = b.a + 2. Why would you want b.a = ><something> to correspond to b.__class__.a = <something>?
That is an implemantation detail. The only answer that you are given means nothing more than: because it is implemented that way. > I'm not saying that it couldn't, if that was the model for inheritance you > decided to use. I'm asking why would you want it? What is your usage case > that demonstrates that your preferred inheritance model is useful? It has nothing to do with a model for inheritance, but with a model of name resolution. The hierarchie of searching an instance first in an object and then in a class isn't that different from searching first in a local namespace and then in a more global namespace. When we search names in a function we don't resolve the same name in different name spacese each occurence of the same name in the same function occurs in the same namespace. But with class variables we can have that one and the same name on a line refers to two different namespaces at the same time. That is IMO madness. You may argue that the madness is of little importance, you can argue that because of the current implementation little can be done about it. But I don't see how one can defend it as sane behaviour. -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
