> > > The KeyError exception doesn't apply repr() to its argument. That's
> > > annoying in cases like this:
> > >
> > > >>> a = {}
> > > >>> a['']
> > > Traceback (most recent call last):
> > > File "<stdin>", line 1, in ?
> > > KeyError
> > > >>>
> > >
> > > Should this be fixed? How? (I guess we could add a KeyError__str__
> > > method to exceptions.c that applies repr().)
> > >
> > > I've got a feeling this is a feature, but not a very useful one.
> >
> > I take it back. args[0] being the actual key that failed is a
> > feature. str() not using repr() on args[0] is a bug. I'll fix it.
> >
>
> What is args[0]?
args is the name of the instance variable that most exceptions use to
store the arguments that were passed to them in the raise statement
(or equivalent C API). It is a tuple. Examples:
>>> a = KeyError()
>>> a.args
()
>>> a = KeyError(1)
>>> a.args
(1,)
>>> a = KeyError(1,2,3)
>>> a.args
(1, 2, 3)
>>> try:
{}['']
except KeyError, k:
print k.args
('',)
>>>
> Are you saying that dicts use repr() instead of str() to
> get the key value when accessing?
No, I'm saying that str(KeyError('foo')) should return repr('foo')
rather than 'foo' as it does now. See current CVS. :-)
--Guido van Rossum (home page: http://www.python.org/~guido/)
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