Hi Dominik,
There's an existing "typing" issue open for this:
https://github.com/python/typing/issues/159
You may meet more people interested in discussing additions to the typing
module in the typing-sig mailing list.
Finally, be aware that PEP 585 is a draft and not even one that's submitted
for review -- ATM it's just a bunch of ideas by one person.
--Guido
On Wed, Aug 28, 2019 at 12:13 PM Dominik Vilsmeier <dominik.vilsme...@gmx.de>
wrote:
> Usually slices are created with integers such as `foo[1:5]`. However
> slices are not restricted to having integers for the `start, stop, step`
> parameters and thus can be used with any types. The most prominent example
> is probably `pandas` which allows slicing by index (and the index can be
> `str` for example):
>
> df = pd.DataFrame([[0], [1], [2]], index=list('abc'), columns=['x'])
> print(df.loc['a':'b']) # The first two items, 'a' and 'b' inclusive.
>
> In one of my projects I also employed the slice syntax in a similar way.
> Sometimes more fine-grained control is desired, e.g. only allowing `str`
> slices and not `int` slices. For that purpose it would be constructive to
> explicitly indicate the type:
>
> class Foo:
> def __getitem__(self, index: Slice[str]):
> pass
>
> foo = Foo()
> foo[1:5] # type checker complains
> foo['foo':'bar'] # no complaints here
>
> The syntax would be somewhat similar to `slice` itself, with the
> difference that `Slice[T]` is similar to `Slice[T, T]`, i.e. specifying
> both the `start` and `stop` type.
>
> Now with [PEP 585](
> https://www.python.org/dev/peps/pep-0585/#importing-of-typing) using
> `slice` directly in annotations seems to be the preferred way, so I'm not
> even sure whether it is realistic to ask for such a new type being added to
> `typing`? Then, what else would it require for this idea to become part of
> the language (if accepted)?
>
> Best regards,
> Dominik
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--
--Guido van Rossum (python.org/~guido)
*Pronouns: he/him/his **(why is my pronoun here?)*
<http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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