[Python-Dev] Re: Exceptional inheritance patterns (original) (raw)

Michael Hudson mwh at python.net
Fri Aug 6 12:16:10 CEST 2004

Holger Krekel <pyth at devel.trillke.net> writes:

Greg Ewing wrote:

> My point is that I like to regard try/except as a mechanism for > "out-of-band" objects. Guidos "should be shot" seems to indicate he > sees try/except only useful/applicable to exception-handling.

If the root exception class were called something else, such as 'Raisable', would that make you feel better? Yes, I certainly wouldn't object. I guess this would mean 'Exception' would derive from Raisable because Exception itself should probably not go away. Hey, strings could inherit from Raisable, too! Just kidding :-)

I would like an exception class that almost exceptions except KeyboardInterrupt, SystemExit and -- maybe -- RuntimeError and MemoryError inherited from.

except ExceptionsButThoseNastyOnesIDontWantToCatch: pass

?

Then again, i think Python has a tradition of not requiring inheritance but just behaviour. And doesn't this whole issue only exist because "raise X" with X being a class and autoinstantiated is allowed?

I would say that it's more because it's useful to organize exceptional conditions in a tree like hierarchy and inheritance is a usable way to do this. The fact that arranging things into tree like hierarchies isn't what inheritance is usually used for in Python (unlike many other languages) is what creates the dissonance, IMHO.

Well, anyway, let's not add too much to the current python-dev traffic with this issue. I think it has been brought up a couple of times already.

Indeed, I think someone said what I just said above in this thread already :-)

Hey, i have an idea: why not create a python-syntax mailing list (or python-hell :-) ?

I think I've suggested that before :-)

Today is the first day I remember where there are more new messages waiting for me in python-dev than comp.lang.python!

Cheers, mwh

-- "The future" has arrived but they forgot to update the docs. -- R. David Murray, 9 May 2000

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