[Python-Dev] Accepting PEP 560 -- Core support for typing module and generic types

[Serhiy Storchaka]

15.12.17 02:25, Yury Selivanov пише:
> My motivation to add the slot wasn't the performance: it's just not
> possible to have a class-level __getitem__ on types defined in C. The
> only way is to define a base class in C and then extend it in
> pure-Python.  This isn't too hard usually, though.

What are problems? How this differs from __sizeof__ and __getstate__?