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.