[Python-ideas] Control Flow - Never Executed Loop Body

[Henshaw, Andy]

> -----Original Message-----
> 
> On Mon, Mar 21, 2016 at 7:01 PM, Stephen J. Turnbull
> <stephen at xemacs.org> wrote:
> >     item = _sentinel = object()
> >     for item in iterable:
> >         # do for each item
> >     if item is _sentinel:
> >         # do exactly when iterable raises StopIteration on the first
> > pass
> 
> What if 'iterable' is locals().values()? Can you, with perfect reliability,
> recognize that case? AIUI this is exactly why next() and
> __next__() are defined to "return a value or raise", rather than "return a
> value or return a magic no-more-values value", because there's always the
> possibility that the no-more-values value is a legitimately-yielded value.
> 
> Maybe this situation isn't important enough or common enough to justify
> dedicated syntax, but it's definitely a possibility.
> 
> ChrisA

is_empty = True
for item in iterable:
    is_empty = False
    # do for each item
if is_empty:
    # do exactly when iterable raises StopIteration on the first

Maybe I'm missing something, but this seems to be an unnecessary addition.

Andy