[Python-Dev] [Python-3000] Warning for 2.6 and greater

Anthony Baxter anthony at interlink.com.au
Fri Jan 12 10:03:55 CET 2007


On Friday 12 January 2007 19:19, Martin v. Löwis wrote:
> Georg Brandl schrieb:
> > It has always been planned that in those cases that allow it,
> > the new way to do it will be introduced in a 2.x release too,
> > and the old way removed only in 3.x.
>
> What does that mean for the example James gave: if dict.items is
> going to be an iterator in 3.0, what 2.x version can make it
> return an iterator, when it currently returns a list?
>
> There simply can't be a 2.x version that *introduces* the new
> way, as it is not merely a new API, but a changed API.

There's a couple of ways I see it - we could add a "-3" command line 
flag to enable 3.x compat, or maybe a from __future__ statement. 
Although the latter would be a global thing, which is different to 
how all existing from __future__s work, so probably not good.

I don't see a path forward that doesn't involve something painful, 
so long as 3.0 is going to be the clean break. As I mentioned, 
though, I'd like as far as possible to make it so that 2.6 (with a 
flag) can be at least vaguely compatible with 3.0.

Anthony
-- 
Anthony Baxter     <anthony at interlink.com.au>
It's never too late to have a happy childhood.


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