is this a bug?

[Brian Quinlan]

> I apologize if this has been brought to the attention of this
> group before. Maybe I did misunderstand the use of the 'is'
> operator, but then how it is supposed to work?

There is a difference between the "is" and "==" operators:
"==" assess equivalence
"is" assess identity

So "is" will return 1 iff the underlying objects being compared are
the same objects. There is a bit of a gotcha here because Python will
try to reuse objects when it can do so e.g.

>>> a = 1
>>> b = 1
>>> a is b # small numbers are precreated for reuse
1
>>> a = 1000
>>> b = 1000
>>> a is b # large ones are not
0

The bottom line is that you should rarely use the "is" operator except
when testing if an object is None (there is only one None object in
Python).

Cheers,
Brian