def emptygen():
    # Or other more meaningful generator
    raise StopIteration
    yield

def wrap(gen):
    next(gen)
    print("This should be printed or StopIteration raised.")
    while True:
        try:
            yield next(gen)
        except StopIteration as exc:
            return

items = wrap(emptygen())
for item in items:
    print(item)

print("End.")

I don't see the bug here.

Your for loop calls wrap.  Wrap calls emptygen.  Emptygen raises a StopIteration exception.  That exception is of course propagated upward (it isn't caught by wrap), and the loop stops.

OK, thanks for explanation.

The behaviour is still strange, because when I delete try...except clause
from wrap, the StopIteration exc from emptygen terminates the program with
traceback.

On Tue, Dec 4, 2012 at 9:14 PM, R. David Murray <report@bugs.python.org>wrote:

>
> R. David Murray added the comment:
>
> I don't see the bug here.
>
> Your for loop calls wrap.  Wrap calls emptygen.  Emptygen raises a
> StopIteration exception.  That exception is of course propagated upward (it
> isn't caught by wrap), and the loop stops.
>
> ----------
> nosy: +r.david.murray
> resolution:  -> invalid
> stage:  -> committed/rejected
> status: open -> closed
>
> _______________________________________
> Python tracker <report@bugs.python.org>
> <http://bugs.python.org/issue16610>
> _______________________________________
>

The only way I was able to replicate that result was by removing the entire try/except block, including the yield.  In that case, wrap is no longer a generator, so the exception is raised before you enter the for loop.

Thank you, I wasn't paying attention enough. It works as you describe.

On Tue, Dec 4, 2012 at 9:46 PM, R. David Murray <report@bugs.python.org>wrote:

>
> R. David Murray added the comment:
>
> The only way I was able to replicate that result was by removing the
> entire try/except block, including the yield.  In that case, wrap is no
> longer a generator, so the exception is raised before you enter the for
> loop.
>
> ----------
>
> _______________________________________
> Python tracker <report@bugs.python.org>
> <http://bugs.python.org/issue16610>
> _______________________________________
>