[Python-ideas] namedtuple literals [Was: RE a new namedtuple]

[Ethan Furman]

On 07/26/2017 09:05 AM, Nick Coghlan wrote:
> On 26 July 2017 at 11:05, Steven D'Aprano <steve at pearwood.info> wrote:

>> I don't see any way that this proposal can be anything by a subtle
>> source of bugs. We have two *incompatible* requirements:
>>
>> - we want to define the order of the fields according to the
>>    order we give keyword arguments;
>>
>> - we want to give keyword arguments in any order without
>>    caring about the field order.
>>
>> We can't have both, and we can't give up either without being a
>> surprising source of annoyance and bugs.
>
> I think the second stated requirement isn't a genuine requirement, as
> that *isn't* a general expectation.

I have to agree with D'Aprano on this one.  I certainly do not *expect* keyword argument position to matter, and it 
seems to me the primary reason to make it matter was not for dicts, but because a class name space is implemented by dicts.

Tuples, named or otherwise, are positional first -- order matters.  Specifying

     point = ntuple(y=2, x=-3)

and having point[0] == 3 is going to be bizarre.  This will be a source for horrible bugs.

--
~Ethan~