[Python-Dev] PEP 409 update [was: PEP 409 (original) (raw)

Ethan Furman ethan 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·sis noun \i-ˈlip-səs, e-
plural el·lip·ses-ˌsēz
Definition of ELLIPSIS 1 a : 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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