Raising objects

[Aahz]

In article <iZ6sa.46825$K35.1342758 at news2.tin.it>,
Alex Martelli  <aleax at aleax.it> wrote:
>
>I would explain my desiderata differently: raising any instance
>of NewException raises it; raising any subclass of NewException
>instantiates it (optionally with the provided argument[s]) and
>raises the resulting instance.
>
>So, the exception that is propagating is ALWAYS an instance of
>NewException.  An except clause catches an exception E, if and
>only if it names a type of which E is an instance.

Note that aside from string exceptions, this is pretty close to the way
it already works:

class C(Exception):
    pass

print type(C)
print type(C())
try:
    raise C
except C, e:
    # e is an instance even though we raised the class
    print type(e)

This is another reason why new-style classes can't be accepted yet:
there's no reliable way to tell the distinction between class and
instance.

(I'm sure Alex already knows this; I'm just commenting for the sake of
people reading along.)
-- 
Aahz (aahz at pythoncraft.com)           <*>         http://www.pythoncraft.com/

"In many ways, it's a dull language, borrowing solid old concepts from
many other languages & styles:  boring syntax, unsurprising semantics,
few automatic coercions, etc etc.  But that's one of the things I like
about it."  --Tim Peters on Python, 16 Sep 93