[Python-Dev] == on object tests identity in 3.x - list delegation to members?

[Chris Angelico]

On Mon, Jul 14, 2014 at 2:23 AM, Steven D'Aprano <steve at pearwood.info> wrote:
>> We will see
>> later that that happens. Further, when comparing float NaNs of the same
>> identity, the list implementation forgot to special-case NaNs. Which
>> would be a bug, IMHO.
>
> "Forgot"? I don't think the behaviour of list comparisons is an
> accident.

Well, "forgot" is on the basis that the identity check is intended to
be a mere optimization. If that were the case ("don't actually call
__eq__ when you reckon it'll return True"), then yes, failing to
special-case NaN would be a bug. But since it's intended behaviour, as
explained further down, it's not a bug and not the result of
forgetfulness.

ChrisA