[Python-Dev] redefining is (original) (raw)

Andrew Koenig ark-mlist at att.net
Fri Mar 19 17:40:57 EST 2004

> 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.

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