On Jan 18, 2008 12:27 AM, Christian Heimes <[EMAIL PROTECTED]> wrote: > Guido van Rossum wrote: > > Oh, you won't. Just don't use the -3 command-line flag and don't put > > "from __future__ import <whatever>" at the top of your modules, and > > you won't have to change your ways at all. You can continue to > > distribute your packages in 2.5 syntax that will also work with 2.6, > > and your users will be happy (as long as they don't want to use your > > code on 3.0 -- but if you want to give them that, *that* is when you > > will finally be forced to face the issue. :-) > > from __future__ import bytes ? What should the __future__ statement change? > > * "" returns unicode instead of str > * b"" is allowed and returns bytes (a new subclass of str) > * u"" is still allowed and returns unicode, too. > * The str built-in is not available.
I don't think any of that is necessary. I would rather have the following two in the language by default (see my response to Terry and Raymond): bytes is an alias for str (not even a subclass) b"" is an alias for "" > > Note that I believe that the -3 flag should not change semantics -- it > > should only add warnings. Semantic changes must either be backwards > > compatible or be requested explicitly with a __forward__ import (which > > 2to3 can remove). > > Agreed! Should the -3 flag also warn about deprecated features which can > easily migrated with 2to3? In the past a warning for `` (back ticks) > were added. The feature is deprecated but the migration is very simple. Personally, I think such warnings are misguided. -3 should augment 2to3, not duplicate its work. > A 2to26 fixer may be worth implementing, too. It could migrate minor > changes like `` -> repr and "except egg, spam" -> "except egg as spam". 2to3 with selected options can do that already. But again, I don't see the point -- 2.6 code can just use 2.5 syntax and 2to3 will take care of the migration. There is only one thing I'd like -3 to warn about regarding except clauses: if the 'err' variable is used past the end of the except clause. That is a true semantic change that 2to3 cannot easily fix or flag. Consider this an example of how 2to3 and -3 should augment each other. -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
