On Thu, Aug 12, 2021 at 09:57:06AM -0400, Ricky Teachey wrote:

> This got me thinking just now: allowing ellipses instead of None for the
> first two arguments of the slice() constructor might be a neat idea.

Like this?

>>> obj = slice(..., ..., 5)
>>> print(obj)
slice(Ellipsis, Ellipsis, 5)

The arguments to slice can be anything you like.

>>> slice({'a': object()}, int, ('spam', 'eggs'))
slice({'a': <object object at 0x7f0067ed9420>}, <class 'int'>, ('spam', 'eggs'))

and the interpretation is entirely up to the class:

>>> class C:
...     def __getitem__(self, obj):
...             return obj
...
>>> C()["Hello world!":[]:2.5j]
slice('Hello world!', [], 2.5j)

Aside from the use of a literal `...` for Ellipsis, which is a lot more
recent, this behaviour goes back to Python 1.5 or older. Slices have
always been liberal about what they accept.


--
Steve