[Python-Dev] GeneratorExit inheriting from Exception

Should GeneratorExit inherit from Exception or BaseException?

Currently, a generator that catches Exception and continues on to yield another value can't be closed properly (you get a runtime error pointing out that the generator ignored GeneratorExit).

The only decent reference I could find to it in the old PEP 348/352 discussions is Guido writing [1]:

(at that point in the conversation, I believe bare except was considered the equivalent of "except Exception:")

While I agree with what Guido says about GeneratorExit being a bug if it reaches the outer level of an app, it seems like a bit of a trap that a correctly written generator can't write "except Exception:" without preceding it with an "except GeneratorExit:" that reraises the exception. Isn't that exactly the idiom we're trying to get rid of for SystemExit and KeyboardInterrupt?

Regards, Nick.

[1] http://mail.python.org/pipermail/python-dev/2005-August/055173.html

Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia

         http://www.boredomandlaziness.org