Not a bad idea. On Wed, Feb 1, 2012 at 12:53 PM, Terry Reedy <tjre...@udel.edu> wrote: > On 2/1/2012 3:07 PM, Guido van Rossum wrote: >> >> On Wed, Feb 1, 2012 at 10:48 AM, Ethan Furman<et...@stoneleaf.us> wrote: >>> >>> Guido van Rossum wrote: >>>> >>>> >>>> Hm... Reading this draft, I like the idea of using "raise X from >>>> None", but I still have one quibble. It seems the from clause sets >>>> __cause__, and __cause__ can indicate three things: (1) print >>>> __cause__ (explicitly set), (2) print __context__ (default), (3) print >>>> neither (raise X from None). For (1), __cause__ must of course be a >>>> traceback object. >>> >>> >>> >>> Actually, for (1) __cause__ is an exception object, not a traceback. >> >> >> Ah, sorry. I'm not as detail-oriented as I was. :-) >> >>>> The PEP currently proposes to use two special >>>> values: False for (2), None for (3). To me, this has a pretty strong >>>> code smell, and I don't want this pattern to be enshrined in a PEP as >>>> an example for all to follow. (And I also don't like "do as I say, >>>> don't do as I do." :-) >>> >>> >>> >>> My apologies for my ignorance, but is the code smell because both False >>> and >>> None evaluate to bool(False)? >> >> >> That's part of it, but the other part is that the type of __context__ >> is now truly dynamic. I often *think* of variables as having some >> static type, e.g. "integer" or "Foo instance", and for most Foo >> instances I consider None an acceptable value (since that's how >> pointer types work in most static languages). But the type of >> __context__ you're proposing is now a union of exception and bool, >> except that the bool can only be False. > > > It sounds like you are asking for a special class > __NoException__(BaseException) to use as the marker. > > -- > Terry Jan Reedy > > > _______________________________________________ > 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/guido%40python.org
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