[Python-ideas] slice[] to get more complex slices

[Paul Moore]

On 23 July 2018 at 13:19, Todd <toddrjen at gmail.com> wrote:
> On Mon, Jul 23, 2018 at 7:24 AM, Paul Moore <p.f.moore at gmail.com> wrote:
>>
>> On 23 July 2018 at 11:31, Jeroen Demeyer <J.Demeyer at ugent.be> wrote:
>> > On 2018-07-23 12:24, Jeroen Demeyer wrote:
>> >>
>> >> Another solution that nobody has mentioned (as far as I know) is to add
>> >> additional syntax to the language for that. For example, one could say
>> >> that (1:3) could be used to construct slice(1, 3) directly. The
>> >> parentheses are required to avoid confusion with type hints. I'm not a
>> >> Python language expert, but I don't think that type hints can occur
>> >> inside parentheses like that.
>> >
>> >
>> > And this could be extended to tuples (1:3, 2:4) and lists [1:3, 2:4] of
>> > slices too.
>>
>> I thought the reason the proposal got nowhere was because it's pretty
>> simple to define it yourself:
>>
>> >>> class SliceHelper:
>> ...     def __getitem__(self, slice):
>> ...         return slice
>> ...
>> >>> SH = SliceHelper()
>> >>> SH[1::3]
>> slice(1, None, 3)
>>
>> Did I miss something significant about why this wasn't sufficient?
>>
>> Paul
>
>
> That involves initializing an instance, which doesn't serve any purpose in
> this case and I was hoping to avoid.

Well it serves the purpose that you can do it already in current
Python, rather than needing a core interpreter change and limiting
your code to Python 3.8+ only ;-)

Paul