[Python-Dev] PyObject_RichCompareBool identity shortcut

[Raymond Hettinger]

On Apr 27, 2011, at 7:53 AM, Guido van Rossum wrote:

> Maybe we should just call off the odd NaN comparison behavior?

I'm reluctant to suggest changing such enshrined behavior.

ISTM, the current state of affairs is reasonable.  
Exotic objects are allowed to generate exotic behaviors
but consumers of those objects are free to ignore some
of those behaviors by making reasonable assumptions
about how an object should behave.

It's possible to make objects where the __hash__ doesn't
correspond to __eq__.; they just won't behave well with
hash tables.  Likewise, it's possible for a sequence to
define a __len__ that is different from it true length; it
just won't behave well with the various pieces of code
that assume collections are equal if the lengths are unequal.

All of this seems reasonable to me.


Raymond