Exceptions as New Style Classes

[Steven Taschuk]

Quoth Carl Banks:
> Steven Taschuk wrote:
> > Quoth Carl Banks:
  [...]
> >> Why not give exceptions their own metaclass?  So if type(x) is
> >> ExceptionMetaclass, it's a class.  If type(type(x)) is
> >> ExceptionMetaclass, it's an instance.  Otherwise, it's illegal to
> >> raise it.
  [...]
> > I'm not sure what it gains us, though, over the idea of mandatory
> > inheritance from Exception.  Am I missing something?
> 
> Probably not much, unless you think you want to raise exceptions that
> aren't subclasses of Exception.

I would have thought that having to raise instances of classes
which are instances of ExceptionMetaclass would be just as onerous
as having to raise instances of Exception.

    class MyRaisable(Exception):
        # ...

    class MyRaisable(object):
        __metaclass__ = ExceptionMetaclass
        # ...

I suppose Exception could have behaviour you don't want, in which
case the latter might be preferable.

-- 
Steven Taschuk                            staschuk at telusplanet.net
"Our analysis begins with two outrageous benchmarks."
  -- "Implementation strategies for continuations", Clinger et al.