On Oct 1, 2019, at 16:01, Christopher Barker <pythonchb@gmail.com> wrote:

> But I can’t see an argument that something called Subscriptable could (or should) actually mean indexable rather than subscriptable.

Now we are getting into naming things, which is hard, but not the critical step.

But as you point out, it’s actually not that clear exactly what the OP (or anyone else advocating for a new ABC) wants.

Granted. Maybe I’m giving too much slack here because of who the OP is, assuming he will have a good answer to these questions as soon as people stop debating irrelevant stuff about whether the whole design of Python needs to be redone from scratch and asks him for those answers…

Conceptually, all of these things make sense:

 * Subscriptable, which can be implicitly checked.
 * Indexable and Keyable, which cannot be implicitly checked, which would inherit from Subscriptable, and would also be superclasses to Sequence and Mapping respectively (which also can’t be implicitly checked)

Practically, nobody has asked for Indexable and Keyable, and someone who generally knows what he’s talking about has asked for Subscriptable. But that’s just the start of the discussion, not the end.