[Python-Dev] GeneratorExit inheriting from Exception (original) (raw)

Georg Brandl g.brandl at gmx.net
Sat Mar 18 16:31:13 CET 2006

Barry Warsaw wrote:

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.)

Cool! That's so far the clearest solution. An additional bonus is that except statements look nicer:

except: # still catches all Exceptions, just like except Exception:

except Error: # is what you normally should do

Cheers, Georg

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