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

Andrew Koenig ark-mlist at att.net
Fri Mar 19 14:19:39 EST 2004

The problem (if there is any) with 'is' is that it exposes implementation details, therefore it should not be used unless on really knows what one is doing.

Yes. Also, I think that in general, operations that should be used only by people who really know what they're doing should be harder to express.

And 'if obj is None' gains performance by relying on one of these.

So I would consider 'if obj == None' correct, but unoptimized code.

Actually, it's incorrect, because obj could be of a class that redefines == to yield True in that case.

More information about the Python-Dev mailing list