On Sat, 2006-03-18 at 22:53 +1000, Nick Coghlan wrote:
Should GeneratorExit inherit from Exception or BaseException?
Actually, this prompts me to write about an issue I have with PEP 352. I actually don't think it's necessary (yes, I know it's already in the tree).
What I would much rather is is for StandardError to be renamed Error, for Exception to remain the base class of the exception hierarchy, and for KeyboardInterrupt to be moved to inherit directly from Exception. GeneratorExit, SystemExit, and StopIteration would continue to inherit from Exception.
The reasoning is this: anything that can be raised is an Exception. Not all Exceptions are Errors. Anything that signals an error condition is an Error, and anything that signals a warning condition is a Warning. Thus the basic hierarchy /ought/ to be:
Exception +- KeyboardInterrupt +- GeneratorExit +- SystemExit +- StopIteration +- Error | +- ImportError | +- (etc.) | +- Warning +- UserWarning +- (etc.)
Use defined errors should inherit from Error, not Exception. With this, "except Exception" would be a synonym for bare except, while "except Error" would be the standard idiom for letting non-error exceptions pass through.
I don't know whether this is possible for Python 2.5, but I think it should be what we strive for for Py3K, and I do not think BaseException is at all necessary.