[Python-Dev] namedtuple implementation grumble

[Nick Coghlan]

On 9 Jun 2014 10:04, "Raymond Hettinger" <raymond.hettinger at gmail.com>
wrote:
>
>
> On Jun 7, 2014, at 6:25 AM, R. David Murray <rdmurray at bitdance.com> wrote:
>
>>> I guess I could duck-type it based on the _fields attribute but that
>>> feels implicit and fragile.
>>>
>>> What do you guys suggest?
>>
>>
>> I seem to remember a previous discussion that concluded that duck typing
>> based on _fields was the way to go.  (It's a public API, despite the _,
>> due to name-tuple's attribute namespacing issues.)
>
>
> Yes.  That is the recommended approach.
>
> IIRC that was Guido's suggestion rather than creating an abstract
> base class for a named tuple (any tuple-like class with indexable
> elements that are also accessible using named attributes).

Given the somewhat periodic recurrence of the question, might it be worth
making an ABC after all, with "subclass of tuple with a _fields attribute"
as its default check?

"isinstance(obj, collections.NamedTupleABC)" is quite a bit more
self-documenting than "isinstance(obj, tuple) and hasattr(obj, '_fields')"

Cheers,
Nick.

>
>
> Raymond
>
>
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