Should NamedTuple rely on dict being oredered?

[ilevkivskyi]

Currently, NamedTuple relies on the fact that dict is ordered in Python 3.6. However, (if I remember correctly) it was decided at some point that the ordered nature of dict is a CPython implementation detail. The question is should we explicitly use an OrderedDict instead?

[gvanrossum]

How exactly does it depend on that? IIRC you can trust that the namespace arg to __new__ is ordered -- either it's a dict and the dict implementation is ordered, or else it's an OrderedDict.

[ilevkivskyi]

@gvanrossum It actually depends on __annotations__ being ordered. The point is that if one writes:

class C:
    x: int
    y: str

then x and y don't appear in the class namespace. Actually, now I am thinking maybe it makes sense to require __annotations__ to be ordered? (Fortunately, PEP 526 is still provisional, so that it could be updated.)

[gvanrossum]

Yes, esp. since there are no code changes needed.