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[Python-Dev] PEP 409 update [was: PEP 409 - final?]
Nick Coghlanncoghlan at gmail.com
Fri Feb 3 01:34:24 CET 2012
On Fri, Feb 3, 2012 at 10:04 AM, Guido van Rossum <guido at python.org> wrote:> On Thu, Feb 2, 2012 at 3:41 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:>> On Fri, Feb 3, 2012 at 9:32 AM, Yury Selivanov <yselivanov.ml at gmail.com> wrote:>>> In my opinion using Ellipsis is just wrong. It is completely>>> non-obvious not only to a beginner, but even to an experienced>>> python developer. Writing 'raise Something() from None'>>> looks less suspicious, but still strange.>>>> Beginners will never even see it (unless they're printing out>> __cause__ explicitly for some unknown reason). Experienced devs can go>> read language reference or PEP 409 for the rationale (that's one of>> the reasons we have a PEP process).>> I somehow have a feeling that Yury misread the PEP (or maybe my +1) as> saying that the syntax for suppressing the context would be "raise> <exception> from Ellipsis". That's not the case, it's "from None".Oh right, that objection makes more sense.FWIW, I expect the implementation will *allow* "raise exc fromEllipsis" as an odd synonym for "raise exc". I'd want to allow"exc.__cause__ = Ellipsis" to reset an exception with a previously set__cause__ back to the default state, at which point the synonymfollows from the semantics of "raise X from Y" as syntactic sugar for"_exc = X; _exc.__cause__ = Y; raise _exc"Cheers,Nick.-- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia
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