[Python-Dev] PEP 479

[Jim J. Jewett]

I have a strong suspicion that I'm missing something; I have been
persuaded both directions too often to believe I have a grip on the
real issue.

So I'm putting out some assumptions; please tell me if I'm wrong, and
maybe make them more explicit in the PEP.

(1)  The change will only affect situations where StopIteration is
currently raised as an Exception -- i.e., it leaks past the bounds of
a loop.

(2)  This can happen because of an explicit raise StopIteration.  This
is currently a supported idiom, and that is changing with PEP 479.

(2a)  Generators in the unwind path will now need to catch and reraise.

(3)  It can also happen because of an explicit next statement (as
opposed the the implicit next of a loop).
This is currently supported; after PEP 479, the next statement should
be wrapped in a try statement, so that the intent will be explicit.

(4)  It can happen because of "yield from" yielding from an iterator,
rather than a generator?

(5)  There is no other case where this can happen?  (So the generator
comprehension case won't matter unless it also includes one of the
earlier cases.)

-jJ