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[Python-Dev] PEP 409 update [was: PEP 409 - final?]
Ethan Furmanethan at stoneleaf.us
Fri Feb 3 20:03:20 CET 2012
Yury Selivanov wrote:> On 2012-02-03, at 1:20 PM, Guido van Rossum wrote:>> Please. Let's stop this. There is no known use case to ever write>> that. We're just not putting specific measures to prevent it. Writing>>>>>>> a = ...>> Is likewise cute but not very informative. But it is valid syntax.>> Well, right now you'll get TypeError if you want to raise an exception> from something that is not an exception. 'raise from None' will> loosen the check allowing None values, in the 'raise from' statement,> but that should be it.>> To achieve the same effect as 'raise from ...' just do> 'e.__cause__ = ...'.>> On the question of using Ellipsis instead of some new singleton like> __NoContext__: how's Ellipsis semantically related to exceptions after> all?Merrian Webster says:---------------------el·lip·sisnoun \i-ˈlip-səs, e-\plural el·lip·ses\-ˌsēz\Definition of ELLIPSIS1a : the omission of one or more words that are obviously understood but that must be supplied to make a construction grammatically complete---------------------Relation to exceptions:Two places to look: __context__ and __cause__Priority? __cause__When do we check __context__? if __cause__ is omitted (or Ellipsis)~Ethan~
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