With lambda, the ban on "return x" in generators can be evaded:

>>> x = lambda: ((yield 1), (yield 2))
>>> list(x())
[1, 2, (None, None)]
>>> dis.dis(x)
  1           0 LOAD_CONST               0 (1)
              3 YIELD_VALUE
              4 LOAD_CONST               1 (2)
              7 YIELD_VALUE
              8 BUILD_TUPLE              2
             11 RETURN_VALUE

Attaching patch?

BTW, how did you find this bug? :)

I didn't find it, but someone from the German Python webforum. :)

Hmm, I wonder why lambda: (yield 1) alone doesn't give [1, None]. (That
should also go into the test case.)

Anyway, perhaps yield in lambdas should be forbidden.

On Sat, Dec 27, 2008 at 11:41 AM, Georg Brandl <report@bugs.python.org> wrote:
>
> Georg Brandl <georg@python.org> added the comment:
>
> I didn't find it, but someone from the German Python webforum. :)
>
> Hmm, I wonder why lambda: (yield 1) alone doesn't give [1, None]. (That
> should also go into the test case.)

Actually, I don't think the return value should even make it's way to
the list. Generator lambdas shouldn't have any return value IMO.

>
> Anyway, perhaps yield in lambdas should be forbidden.

Probably too late now for 2.x and 3.x.

>> Hmm, I wonder why lambda: (yield 1) alone doesn't give [1, None]. (That
>> should also go into the test case.)
>
> Actually, I don't think the return value should even make it's way to
> the list. Generator lambdas shouldn't have any return value IMO.

Yes, I think so too. I just wondered at the seemingly inconsistent
behavior right now.

>> Anyway, perhaps yield in lambdas should be forbidden.
> 
> Probably too late now for 2.x and 3.x.

Right. I'd say go for applying the patch.

Fixed in r67954.