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

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.

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