I really wish that KeyError, AttributeError,  NameError
and IndexError provided clean APIs for getting at the
missing key, name, or index.

(Suggested by Jim Fulton)

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For KeyError, isn't it e.args[0]?

For the others, I suggest that args[0] is the string,
args[1] is the parameter. As a result, those classes need a
__str__ which returns args[0].

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Yes, it's args[0] for KeyError, but Jim objected that this
is a rather obscure protocol; he would prefer to have a
designated attribute.

Will this be revisited for py3k?

I think it would be a good idea to revisit this for py3k, but I'm out of
round tuits.  Anyone else want to tackle this?  It should ideally be
done in such a way that non-core object types can also easily raise
these exceptions with the appropriate attributes, both from C and from
Python.

It looks like issue2651 is the first step for this.  See msg66432. I am merging the nosy lists.

See also #18156, #18163, #18165 and #18166, possibly others?

messages: + msg107340
stage: needs patch