Oh yes , I see. Seems like almost everybody think using the [...] syntax to define reusable slices is a good idea, the discussion is where this could be implemented, knowing that numpy.s_ already exists.

Discussion is not easy to follow, with the patch almost accepted then delayed then rejected, in a very short amount of time.

In particular, it's not clear why direct indexing of slice type (not instance) was not chosen. It was the first proposal, and here again Todd's choice. it was silently skipped/changed to slice.literal then moved to operators, at least that's the impression I got reading  https://bugs.python.org/issue24379 ...

Not sure slice[1::3] can be done, but this has my preference too: it's the most direct exposure I can think of...