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Mon Feb 16 20:07:58 EST 2004 · https://mail.python.org/pipermail/python-dev/2004-February/042590.html

> Martin:
> 
> > Of these, there are two categories of objects:
> > - values:
> > - identity objects:
> > 
> > Values fall into two further categories:
> > - immutable values:
> > - mutable values:

[Greg]
> All these rules can be boiled down to:
> 
>   * Objects which compare equal should hash equal.
>   * The notion of equality should not change over the
>     lifetime of the object.
> 
> There's no need to mention mutability at all.

Actually, think the very definition of a mutable object may be one
whose equality can change over its lifetime.

As you pointed out, we should talk about (im)mutable objects, not
types, because (e.g.) tuples can contain lists.

--Guido van Rossum (home page: http://www.python.org/~guido/)

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[Python-Dev] bool does not want to be subclassed?