On Tue, Nov 3, 2009 at 11:06 PM, Lennart Regebro regebro@gmail.com wrote:
I should maybe point out that although I'm generally +1 on backporting, I'm not specifically anything on backporting the nonlocal keyword. There are probably things that would help more from a compatibility standpoint than that.
For example, from __future__ import unicode_literals doesn't switch the types. So this code will rais an assertion error in 2.6.
from __future__ import unicode_literals assert isinstance("fghjkl", str)
While it of course will run fine in 3.0. Now this has a fairly trivial workaround or two, but still.
I also would really like to see a real port of the bytes class to 2.6, but I have a vague memory that there was some reason that wouldn't work.
There are many interfaces that return a str instance which should become a bytes instance for code that is bytes-aware, but should stay a str instance (which after all has the same representation) for code that is not bytes-aware. In 3.x it's easy, such interfaces always return bytes instances. But in 2.x, it would have to be context-aware, and there are many reasons why that can't work. (E.g. an object could be shared between two modules, one of which is bytes-aware, while the other is not. Or a call could be made by a module that isn't bytes-aware and the return value passed to a module that is bytes-aware. Or vice versa. It's a mess unless *everyone* is bytes-aware, which is the 3.x world.)