Travis Oliphant <oliphant@ee.byu.edu> writes:
Thanks for the tip. I think I figured out the problem, and it was my misunderstanding of how types inherit in C that was the source of my problem.
Basically, Python is doing what you would expect, the mp_item is used for __getitem__ if both mp_item and sq_item are present. However, the addition of these descriptors (and therefore the resolution of any comptetion for __getitem__ calls) is done *before* the inheritance of any slots takes place.
Oof. That'd do it.
The new ndarray object inherits from a "big" array object that doesn't define the sequence and buffer protocols (which have the size limiting int dependencing in their interfaces). The ndarray object has standard tp_as_sequence and tp_as_buffer slots filled.
I guess the reason this hasn't come up before is that non-trivial C inheritance is still pretty rare.
The easy fix was to initialize the tp_as_mapping slot before calling PyType_Ready. Hopefully, somebody else searching in the future for an answer to their problem will find this discussion useful.
Well, it sounds like a bug that should be easy to fix. I can't think of a reason to do slot wrapper generation before slot inheritance, though I wouldn't like to bet more than a beer on not having missed something... Cheers, mwh -- There are two kinds of large software systems: those that evolved from small systems and those that don't work. -- Seen on slashdot.org, then quoted by amk