[Python-ideas] for/except/else syntax

[Bruce Leban]

Here you go:
do_except = True
for i in SEQ:
  do_except = False
  A
else:
  if not do_except:
    C  # suite_if_loop_is_not_broken
if do_except:
  B  # suite_if_loop_body_is_not_executed

--- Bruce



On Tue, Oct 6, 2009 at 8:53 PM, Guido van Rossum <guido at python.org> wrote:

> On Tue, Oct 6, 2009 at 8:46 PM, Bruce Leban <bruce at leapyear.org> wrote:
> > Switching gears a bit, here's what I want:
> >
> > for_stmt ::= "for" target_list "in" expression_list ":" suite_loop_body
> > ["except" ":" suite_if_loop_body_is_not_executed] ["else" ":"
> > suite_if_loop_is_not_broken]
> >
> > The except and else appear in this order to make it clear that except
> takes
> > precedence. If the loop body is not executed at all then both conditions
> are
> > true but it obviously is only useful if except takes precedence.
> > Comments?
>
> I'm sure it's obvious to you what the except clause should do, but it
> isn't to me. :-( Assuming you're not proposing we change the meaning
> of else in the absence of except, and that its meaning together with
> except is a logical extension of this, can you show how we should
> translate a for-loop with an except clause into current Python? Say,
> what would I be writing today to get the exact effect of your proposed
>
> for i in SEQ:
>  A
> except:
>  B
> else:
>  C
>
> ?
>
> --
> --Guido van Rossum (home page: http://www.python.org/~guido/)
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-ideas/attachments/20091006/0b961a48/attachment.html>