On Tue, Oct 8, 2019 at 2:18 PM Anders Hovmöller <bo...@killingar.net> wrote:
>
>
> On 8 Oct 2019, at 20:07, Todd <toddr...@gmail.com> wrote:
>
>
>
> On Tue, Oct 8, 2019 at 1:30 PM Anders Hovmöller <bo...@killingar.net>
> wrote:
>
>>
>>
>> On 8 Oct 2019, at 19:19, Caleb Donovick <donov...@cs.stanford.edu> wrote:
>>
>>
>>
>>> Because
>>>
>>> >>> dict(foo=:1)
>>> File "<string>", line 1
>>> dict(foo=:1)
>>> ^
>>> SyntaxError: invalid syntax
>>>
>>
>> I don't see how that's an argument, we are talking about a syntax
>> extension. Slice builder syntax is only every allowed in a subscript.
>> Edit my original grammar change proposal to:
>>
>> ```
>> subscriptlist: ... | kwargsubscript (',' kwargsubscript )* [',']
>> kwargsubscript: NAME '=' subscript
>> ```
>>
>> Now slices are allowed in keyword arguments.
>>
>>
>> I wasn't making an argument, I was wondering what exactly we are even
>> discussing. It seems like people are inventing new syntax willy nilly in
>> this thread and I am getting very confused :)
>>
>> / Anders
>>
>>
> I thought we were talking about allowing __getitem__ to support keywords.
> I assumed the keywords would use the same syntax as positional values, and
> converting colons to slice objects is part of that syntax. So this isn't
> new syntax, it is just making the positional and keyword syntaxes the same.
>
>
> I don't see it. Can you give examples of all the variations of slicing and
> their keyword equivalent so I understand what you mean? I'll write out the
> slicing variants and you can fill in how it would look with keyword
> arguments:
>
> x[:]
> x[a:]
> x[-a:]
> x[a:b]
> x[-a:b]
> x[a:-b]
> x[-a:-b]
> x[:b]
> x[:-b]
>
>
>
The colon operation would be converted to slices identically to how it is
with positional arguments, it is just that those slices would assigned to
values in a dict (or some other mapping) instead of values in a tuple.
Otherwise it would work exactly the same.
x[:] is x[slice(None, None)]
x[foo=:] is x[foo=slice(None, None)]
x[a:] is x[slice(a, None)]
x[foo=a:] is x[foo=slice(a, None)]
x[-a:] is x[slice(-a, None)]
x[foo=-a:] is x[foo=slice(-a, None)]
x[a:b] is x[slice(a, b)]
x[foo=a:b] is x[foo=slice(a, b)]
x[-a:b] is x[slice(-a, b)]
x[foo=-a:b] is x[foo=slice(-a, b)]
x[a:-b] is x[slice(a, -b)]
x[foo=a:-b] is x[foo=slice(a, -b)]
x[-a:-b] is x[slice(-a, -b)]
x[foo=-a:-b] is x[foo=slice(-a, -b)]
x[:b] is x[slice(None, b)]
x[foo=:b] is x[foo=slice(None, b)]
x[:-b] is x[slice(None, -b)]
x[foo=:-b] is x[foo=slice(None, -b)]
If you look at multiple indices,
x[a, -b:c] is x[a, slice(-b, c)]
x[foo=a, bar=-b:c] is x[foo=a, bar=slice(-b, c)]
_______________________________________________
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at
https://mail.python.org/archives/list/python-ideas@python.org/message/7FAT73WY6CKCCWB2ZQPMZSAXV4CPFJLX/
Code of Conduct: http://python.org/psf/codeofconduct/
