[Python-Dev] Extended Function syntax

[Chermside, Michael]

Oren Tirosh writes:
> Currently, when a generator yields and is never resumed it just dies
> silently. I suggest that it would be resumed one last time with an=20
> AbortIteration exception raised at the yield statement.
     [...]
> The difference is that this exception=20
> based system does not make such a strong guarantee as try/finally - it =

> will be triggered when the iteration is aborted by break, return or an =

> exception in the looping scope but not by a __del__ of a generator=20
> object dropping to refcnt of 0 so it should be "Jythonially correct".

Essentially, you're proposing that we USUALLY but not ALWAYS guarantee
to call __leave__ (aka __exit__). To me, this suffers from the same
problem that your generators patch had... guarantees need to be solid!
In the case of generators, I think it's better saying "yield cannot be
used inside of try-finally" than saying "if yield is used inside of
try-finally then on rare occasions the finally clause may not execute".
Similarly, I think if we plan to use this for problems like resource=20
allocation-deallocation, then we'd better not say "__leave__ will
usually be called" -- that's practically useless. We need a solid
guarantee.

-- Michael Chermside