Quoth Guido van Rossum: [...]
Python usually doesn't care about isinstance relationships but cares about whether the needed protocol is implemented, and this suggests that requiring exceptions to subclass Exception is unPythonic.
This came up in python-list not long ago [1], and I raised (heh) exactly that argument. Alex Martelli counterargued that exceptions are one area in which we *do* usually care about isinstance relationships, since that's how we specify which exceptions to catch. [1] http://mail.python.org/pipermail/python-list/2003-May/160965.html -- Steven Taschuk staschuk@telusplanet.net "I'm always serious, never more so than when I'm being flippant." -- _Look to Windward_, Iain M. Banks