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

Yury Selivanov yselivanov.ml at gmail.com
Fri Feb 3 20🔞53 CET 2012

That's a bit far-fetched. Using same level argumentation we can utilize even 0. raise e from 0 (or -1), and use 0 object instead of Ellipsis.

Anyways, if the PEP is not yet fully approved, I'm minus one on allowing of using anything other than Exception instance or None in 'raise from' statement.

On 2012-02-03, at 2:03 PM, Ethan Furman wrote:

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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