[Python-Dev] Re: redefining is

[Andrew Koenig]

> Objects are equivilant if they are the same type and their states are
> the same
> 
> Objects are interchangable if they are equivilant and their states will
> always be the same (i.e., changes to one are always reflected in the
> other) or if they are equivilant and immutable.

I haven't distinguished between equivalent and interchangeable.  I think
that most people would consider "equivalent" and "interchangeable" to mean
the same thing.

> Objects are identical if they are physically the same (in the sense of
> 'is' currently)

Yes.

> There is also a fourth type:
> 
> Objects are equal if ob1.__eq__(ob2) returns true.

Right.