[Python-Dev] == on object tests identity in 3.x

Ethan Furman ethan at stoneleaf.us
Fri Jul 11 22:54:40 CEST 2014

On 07/11/2014 07:04 AM, Andreas Maier wrote:
> Am 09.07.2014 03:48, schrieb Raymond Hettinger:
>> Personally, I see no need to make the same mistake by removing
>> the identity-implies-equality rule from the built-in containers.
>> There's no need to upset the apple cart for nearly zero benefit.
> Containers delegate the equal comparison on the container to their elements; they do not apply identity-based comparison
> to their elements. At least that is the externally visible behavior.

If that were true, then [NaN] == [NaN] would be False, and it is not.

Here is the externally visible behavior:

Python 3.5.0a0 (default:34881ee3eec5, Jun 16 2014, 11:31:20)
[GCC 4.7.3] on linux
Type "help", "copyright", "credits" or "license" for more information.
--> NaN = float('nan')
--> NaN == NaN
--> [NaN] == [NaN]


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