[Python-Dev] Re: Dangerous exceptions (was Re: Another test_compilermystery)

[Jeremy Hylton]

On Tue, 07 Sep 2004 09:43:53 -0400, Jim Fulton <jim at zope.com> wrote:
> Jeremy Hylton wrote:
> 
> ...
> 
> >  I
> > think it would be easier in principle to put them at a different place
> > in the class hierarchy than to make them some special kind of
> > uncatchable exception.
> 
> Note that we don't want uncatchable exceptions. Rather, we want
> exceptions that aren't caught by bare excepts or very broad
> excepts.  In many cases, we want certain knowledgeable code to be able
> to catch these exceptions.

I agree with half the cause.  There ought to be a decent organization
of the exception class hierarchy so that exceptions like
KeyboardInterrupt are in a special category.  Then an "except
NormalError:" <wink> would catch only the normal errors and not the
special ones.  I don't think bare exception should change it's
meaning; you just shouldn't use it unless it's *really* what you mean.

I think backwards compatibility is a really hard issue for any of
these changes.  It's probably hard to re-arrange the class hierarchy,
but I don't know what practical solution there is to these problems
that doesn't involve breaking some code.  It's even harder to change
bare except, but I don't think that's necessary.

Jeremy