On Mar 29, 2014, at 2:53 PM, Gregory P. Smith <greg@krypto.org> wrote:

On Thu, Mar 27, 2014 at 3:05 PM, Antoine Pitrou <solipsis@pitrou.net> wrote:

On Thu, 27 Mar 2014 18:47:59 +0000
Brett Cannon <bcannon@gmail.com> wrote:
> On Thu Mar 27 2014 at 2:42:40 PM, Guido van Rossum <guido@python.org> wrote:
>
> > Much better, but I'm still not happy with including %s at all. Otherwise
> > it's accept-worthy. (How's that for pressure. :-)
> >
>
> But if we only add %b and leave out %s then how is this going to lead to
> Python 2/3 compatible code since %b is not in Python 2? Or am I
> misunderstanding you?

I think we have reached a point where adding porting-related facilities
in 3.5 may actually slow down the pace of porting, rather than
accelerate it (because people will then wait for 3.5 to start porting
stuff).

I understand that sentiment but that is an unjustified fear. It is not a good reason not to do it. Projects are already trying to port stuff today and running into roadblocks when it comes to ascii-compatible bytes formatting for real world data formats in code needing to be 2.x compatible. I'm pulling out my practicality beats purity card here.

Mercurial is one of the large Python 2.4-2.7 code bases that needs this feature in order to support Python 3 in a sane manner. (+Augie Fackler to look at the latest http://legacy.python.org/dev/peps/pep-0461/ to confirm usefulness)

That looks sufficient to me - the biggest thing is being able to do

"abort: %s is broken" % some_filename_that_is_bytes

and have that work sanely, as well as the numerics. This looks like exactly what we need, but I'd love to test it soon (I'm happy to build a 3.5 from tip for testing) so that if it's not Right[0] changes can be made before it's permanent. Feel encouraged to CC me on patches or something for testing (or mail me directly when it lands).

Thanks!

-gps