[Guido van Rossum] > > Do we really need both __context__ and __cause__?
[Ka-Ping Yee] > Well, it depends whose needs we're trying to meet. > > If we want to satisfy those who have been asking for chaining > of unexpected secondary exceptions, then we have to provide that > on some attribute. > > If we also want to provide the facility that Java and C# provide > with initCause/InnerException, then we need a separate attribute > devoted to explicit chaining. The Java and C# documentation is > clear that the cause/inner exception is to be set only on an > exception that is "caused" or a "direct result" of the primary > exception, which i've taken as a sign that this is an important > distinction. > > I wanted to give a shot at making both camps happy. > > If the two were unified, we'd still be better off than we are > now, but we should be aware that we would not be providing the > functionality that Java and C# provide. But what difference does it make in practice? In first approximation, the only time the context is interesting is when a traceback is printed. Since you propose to print __context__ when __cause__ isn't set, from the POV of the user reading the traceback the effect is the same as if there was only one link (let's call it __cause__) and the APIs for setting it simply override the default. (PS I'm still thinking about the equivalence of the chaining algorithms; I've got a proof sketch in my head but getting the details in email is taking time.) -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
