[Python-Dev] PEP 409 update [was: PEP 409 - final?]

Tim Delaney timothy.c.delaney at gmail.com
Fri Feb 3 04:34:26 CET 2012


On 3 February 2012 13:54, Guido van Rossum <guido at python.org> wrote:

> On Thu, Feb 2, 2012 at 6:49 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:
> > On Fri, Feb 3, 2012 at 12:42 PM, Ethan Furman <ethan at stoneleaf.us>
> wrote:
> >> Nick Coghlan wrote:
> >>>
> >>> FWIW, I expect the implementation will *allow* "raise exc from
> >>> Ellipsis" as an odd synonym for "raise exc".
> >>
> >>
> >> Are we sure we want that?  Raising from something not an exception seems
> >> counter-intuitive (None being the obvious exception).
> >
> > It isn't so much a matter of wanting it as "Is it problematic enough
> > to put any effort into preventing it?" (since allowing it is a natural
> > outcome of the obvious implementation).
>
> I would say yes we want that. It would be strange if you couldn't
> reset a variable explicitly to its default value.


In that case, would the best syntax be:

    raise Exception() from Ellipsis

or:

    raise Exception() from ...

? I kinda like the second - it feels more self-descriptive to me than "from
Ellipsis" - but there's the counter-argument that it could look like noise,
and I think would require a grammar change to allow it there.

Tim Delaney
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