On Fri, Sep 25, 2020 at 6:05 AM Ricky Teachey <ri...@teachey.org> wrote:
> I'd like to hear more about why the empty tuple has been selected as the
> default index.
>
It makes sense to me: if more than one index is passed, they are passed as
a tuple. so many classes need to handle tuples anyway.
What other options are there? I suppose None is a possibility, but None is
a valid dict key, so probably not a great idea. Hmm, so is an empty tuple.
Darn.
I think having no default is a better option, as someone pointed out
already in this thread.
-CHB
>
> On Fri, Sep 25, 2020, 1:07 AM David Mertz <me...@gnosis.cx> wrote:
>
>> Is this a breaking change? It feels borderline.
>>
>> Keyword-only subscripts are permitted. The positional index will be the
>>> empty tuple:
>>> obj[spam=1, eggs=2]
>>> # calls type(obj).__getitem__(obj, (), spam=1, eggs=2)
>>
>>
>> I.e. consider:
>>
>> >>> d = dict()
>> >>> d[()] = "foo"
>> >>> d
>> {(): 'foo'}
>>
>>
>> I don't really object to this fact, and one could argue it's not a
>> breaking change since a built-in dict will simply raise an exception with
>> keyword arguments. However, it does make the empty tuple the "default key"
>> for new objects that will accept keyword indices.
>>
>> --
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>> the lives and control the thoughts of homo faber. Ideas, once born,
>> become abortifacients against new conceptions.
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--
Christopher Barker, PhD
Python Language Consulting
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