[Types-sig] Why have two hierarchies? (*EUREKA!*)

Just van Rossum just@letterror.com
Sat, 5 Dec 1998 20:00:21 +0100

Donald Beaudry wrote:
>But that's too simple to be any fun ;)

I *knew* it! ;-)

>Besides, now you have to answer
>the question of what object is used to represent the bases collection?
>Is it a tuple of objects, or is it just an object?

As far as I'm concerned any sequence object will do. In other words: any
object that implements __getitem__.

>...and what about
>the objects in the collection, what can we expect of them.

- that they have a __bases__ attribute
- that they have a __namespace__ attribute (without one, inheriting
  makes no sense)
- that you can fetch attributes from them.

Nothing more I guess.

>attributes and methods do they have?

I'd say a __getattr__ method.

>What attributes and methods does
>the collection have?

I answered that before: __getitem__...

>Where do we encode the attribute look-up policy
>for our instances?

In a custom __getattr__. That may sound primitive, but that's all there is
to it (as far as I can see). If you define a __getattr__ it will get called
for *all* attribute access: if you want to pretend you're inheriting of
something else than what __bases__ says, go right ahead! Only your
__getattr__ method must be on the __bases__ path.

>You can change the names all you want, but simplifying this mess isnt
>going to be that simple :)

What's the problem? ;-) (Seriously: I *may* just not get it: please