[Python-Dev] redefining is

[Andrew Koenig]

> Okay, but I don't see why that implementation detail is important.

It is important because it causes programs to behave differently on
different implementations.

> > So what I'm claiming is that there should be a way of asking:  Given two
> > objects, is there any way to distinguish them aside from their identity?

> Why do you need to ask that question?  Further more, why is it
> important enough to require a builtin operator?

It certainly doesn't *require* a builtin operator.  I do think, however,
that the proposed comparison is more useful than "is" in most contexts in
which programmers use "is" today.  In particular, programs that use "is" can
easily contain bugs that testing on a particular implementation can never
reveal, and using the proposed comparison instead makes such bugs much less
likely (and perhaps even impossible).