[Python-Dev] PEP 352: Required Superclass for Exceptions (original) (raw)
Nick Coghlan ncoghlan at gmail.com
Fri Oct 28 13:12:42 CEST 2005
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Brett Cannon wrote:
Anyway, as soon as the cron job posts the PEP to the web site (already checked into the new svn repository) have a read and start expounding about how wonderful it is and that there is no qualms with it whatsoever. =)
You mean aside from the implementation of getitem being broken in BaseException*? ;)
Aside from that, I actually do have one real problem and one observation.
The problem: The value of ex.args
The PEP as written significantly changes the semantics of ex.args - instead of being an empty tuple when no arguments are provided, it is instead a singleton tuple containing the empty string.
A backwards compatible definition of BaseException.init would be:
def __init__(self, *args):
self.args = args
self.message = '' if not args else args[0]The observation: The value of ex.message
Under PEP 352 the concept of allowing "return x" to be used in a generator to mean "raise StopIteration(x)" would actually align quite well. A bare "return", however, would need to be changed to translate to "raise StopIteration(None)" rather than its current "raise StopIteration" in order to get the correct value (None) into ex.message.
Cheers, Nick.
- (self.args[0] is self.message) due to the way init is written, but getitem assumes self.message isn't in self.args)
-- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia
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