Thanks for bringing this up. I've added my opinion to the tracker issue -- I think it's a bug and should be fixed. We should have a uniform way of checking for issubclass/isinstance.
--Guido On Fri, May 11, 2012 at 3:33 AM, George-Cristian Bîrzan <gcbir...@gmail.com> wrote: > As per http://bugs.python.org/issue12029 , ABC registration cannot be > used for exceptions. This was introduced in a commit that fixed a > recursion limit problem back in 2008 > (http://hg.python.org/cpython/rev/d6e86a96f9b3/#l8.10). This was later > fixed in a different way and improved upon in the 2.x branch in > http://hg.python.org/cpython/rev/7e86fa255fc2 and > http://hg.python.org/cpython/rev/57de1ad15c54 respectively. > > Applying the fix from the 2.x branch for doesn't make any tests fail, > and it fixes the problem described in the bug report. There are, > however, two questions about this: > > * Is this a feature, or a bug? I would say that it's a bug, but even > if it's not, it has to be documented, since one generally assumes that > it will work. > * Even so, is it worth fixing, considering the limited use cases for > it? This slows exception type checking 3 times. I added a new test to > pybench: > > before: > TryRaiseExceptClass: 25ms 25ms 0.39us 0.216ms > after: > TryRaiseExceptException: 31ms 31ms 0.48us 0.214ms > > However, that doesn't tell the whole story, since there's overhead > from raising the exception. In order to find out how much actually > checking slows down the checking, I ran three timeits, with the > following code: > > 1) > try: raise ValueError() > except NameError: pass > except NameError: pass > except ValueError: pass > > 2) > try: raise ValueError() > except NameError: pass > except ValueError: pass > > 3) > try: raise ValueError() > except ValueError: pass > > Times are in ms: > before after > 1 528.69 825.38 > 2 473.73 653.39 > 3 416.29 496.80 > avgdiff 56.23 164.29 > > The numbers don't change significantly for more exception tests. > > -- > George-Cristian Bîrzan > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > http://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > http://mail.python.org/mailman/options/python-dev/guido%40python.org -- --Guido van Rossum (python.org/~guido) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
