[Python-Dev] readd u'' literal support in 3.3? (original) (raw)

Chris McDonough chrism at plope.com
Fri Dec 9 07:01:10 CET 2011

On Thu, 2011-12-08 at 21:43 -0800, Guido van Rossum wrote:

On Thu, Dec 8, 2011 at 9:33 PM, Chris McDonough <chrism at plope.com> wrote: On Thu, 2011-12-08 at 19:52 -0500, Glyph wrote: > Zooming back in to the actual issue this thread is about, I think the > u""-vs-"" issue is a bit of a red herring, because the real problem > here is that 2to3 is slow and buggy and so migration efforts are > starting to work around it, and therefore want to run the same code on > 3.x and all the way back to 2.5.

Even if it weren't slow, I still wouldn't use it to automatically convert code at install time; a single codebase is easier to reason about, and easier to support. Users send me tracebacks all the time; having them match the source is a wonderful thing. Even though 2to3 was my idea, I am gradually beginning to appreciate this approach. I skimmed the docs for "six" and liked it. But I think the specific proposal of adding u"..." literals back to 3.3 is not going to do much good. If we had had the foresight way back when, we could have added them back to 3.1 and we would have been okay. But having them in 3.3 but not in 3.2 is just adding insult to injury.

AFAICT, at the current pace of porting, lots of authors of existing, popular Python 2 libraries won't be releasing a ported/straddled version any time soon; almost certainly many won't even begin work on a port until after 3.3 is final. As a result, on the supplier side, there will be plenty of code that will eventually work only as a straddle across 2.6, 2.7, and 3.3.

On the consumer side, folks who want to run 2.6/2.7/3.3-only codebases will have the wherewithal to compile their own Python 3 (or use a PPA or equivalent) until the distros catch up.

So I'm not sure why 3.2 not having support for u'' should be a real blocker for the change.

I recommend writing b"...".decode('utf-8'); maybe six's u() does the same?

It does this:

def u(s):
    return unicode(s, "unicode_escape")

That's two Python function calls, of course, which is obviously icky if you use a lot of literals at a nonmodule scope.

More information about the Python-Dev mailing list