On Mar 7, 3:41 pm, [EMAIL PROTECTED] wrote: > On Mar 7, 4:39 pm, DBak <[EMAIL PROTECTED]> wrote: > > > On Mar 7, 1:19 pm, "Chris Mellon" <[EMAIL PROTECTED]> wrote: > > > > On Fri, Mar 7, 2008 at 3:00 PM, DBak <[EMAIL PROTECTED]> wrote: > > > > However I can't do this, because, of course, the name Tree isn't > > > > available at the time that the classes _MT and _Node are defined, so > > > > _MT and _Node can't inherit from Tree. > > > > Not only is the name not defined, the class doesn't even exist yet. > > > Yes, but, well - it certainly isn't usable yet, but some object (that > > will be the class when it is finished) is being built (its __dict__ is > > being populated, etc.) - so there's an object pointer available inside > > the interpreter that could be put somewhere. But this is pedantic - > > you're right, the class really isn't available until after the class > > statement. > > There is no obvious solution-- What do you mean? If there are any at > all, there is significant competition without clear winners. > > dict dictA: > membA= 0 > membB= 0 > > dict dictB: > membC= 0 > > But, if you try to nest them, do you want the rest of the 'dict' at > its outer level evaluated (that's your 'here is the crux'), or only > that point so far? > > dict dictO: > membA= 0 > dict membB: > membC= 0 > membD= membE > membE= 0 > > So, you can't refer to it at all. Especially if membE is defined in > outer scope.
Thanks for your answer. To the extent I understand it: There is a difference between the class statements I was trying to nest, with the inner inheriting from the outer, and your dict example. The main thing is that in the class example - when the inner class is being built (i.e., inside its class statement's block) there is no need (as I understand it) for the parent class to be functional at all WHILE I AM DEFINING METHODS on the inner class. Sure, if the inner class had code to be executed immediately, such as statements setting class attributes on the inner class, and that code used names such that attribute lookup needed to be done, then that might or might not work - it would depend on where the names were defined in the outer class relative to the placement of the inner class statement - exactly like the fact that the order of definition matters when executing code when defining a module: functions defined in a module can, in their body, name functions not yet defined, but assignment statements to module attributes cannot (they get a run time error). But in the case I'm talking about I just want to define methods on the inner class, using names such that when the method is eventually called on an instance of the inner class the attribute lookup will proceed with the outer class being the inner class' parent. Creating instances of the inner class won't happen until after the inner class and the outer class are both fully created (and assigned to their names) so any name lookup using inheritance won't happen until both class objects are fully created, so ... if you could do it ... it would work fine. Anyway, I know it can't be done the way I wanted it - the attribute with the outer class' name hasn't been assigned yet when I need to reference it in the inner class' class statement - so I was just looking to see what the preferred alternative was. Based on the discussion so far it seems I should just forget about using nested classes and flatten everything to the module level, using the __all__ attribute to make it clear to the user of the data structure what pieces of the module he should actually be using. -- David -- http://mail.python.org/mailman/listinfo/python-list
