[Python-Dev] rationale for the no-new-features approach

[Bob Ippolito]

On Mar 10, 2005, at 11:46 PM, Glyph Lefkowitz wrote:

> Bob Ippolito wrote:
>> try:
>>     set
>> except NameError:
>>     from sets import Set as set
>
> Syntactical variations notwithstanding, I think it's a common desire 
> to want to run on at least the last few versions of Python, but take 
> advantage of improvements and not emit deprecation warnings on the 
> latest and greatest.
>
> I am considering releasing a forward-compatibility library for 
> installation alongside applications that need to use multiple versions 
> of Twisted, so they can do it in a style which is closer to the new 
> versions than the old ones: perhaps it might be good practice to start 
> doing this for Python as well?
>
> That way instead of multi-line "except NameError" tests all over the 
> place you can simply have one-liner boilerplate for every module in 
> your project:
>
> 	'from py24compat import *'
>
> Easy to grep/sed for when you're ready to stop supporting old 
> versions, too, for those of you without a copy of the refactoring 
> editor from the 2009 release of PyDev/Eclipse.
>
> The only problem with this idea is that the 2.3 -> 2.4 transition has 
> been extremely smooth for me - there are no new features I desperately 
> want to use, and there are no old features that were deprecated or 
> altered (that I've found yet - knock on wood).  Still, future 
> incompatibilties are inevitable.
>
> Of course I'd also like to echo the thanks to Anthony for having 
> relegated this problem to major releases.

I'm definitely +1 on such a library.  I've cobbled together something 
like it myself:

http://svn.red-bean.com/bob/py2app/trunk/src/altgraph/compat.py

And this monkey-patches readline support in for UTF-16 streams:

http://svn.red-bean.com/bob/unicode/trunk/utf16reader.py

-bob