[Python-Dev] redefining is

[Andrew Koenig]

> > 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.

> Are you saying that most instances of "is" in current Python code
> are incorrect?  If not, what do you mean by more useful?

I strongly suspect that most instances of "is" in current Python code would
not change their meaning, because most instances of "is" use either
singletons or mutable objects.  However, I also think that a number of uses
of "is" that are currently incorrect, sometimes in subtle ways, would become
useful.

As things stand, I think I reluctantly agree that it's too big a change to
consider, because I can certainly imagine programs that might break.
Nevertheless, I still wish that expressions such as "x is 'foo'" did not
silently differ in outcome from one implementation to another.