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From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: proposal: bring nonlocal to py2.x
Date: Mon, 13 Jan 2014 16:26:26 -0500
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Xref: csiph.com comp.lang.python:63864

On 1/13/2014 9:47 AM, Neal Becker wrote:
> py3 includes a fairly compelling feature: nonlocal keywork
[keyword]
> But backward compatibility is lost.

I am not sure what your particular point is. Every new feature, in any 
release, if used, makes code not compatible with earlier releases that 
do not have the feature. Every new feature is compelling to someone, and 
to use it, one must use a version that has it.

> It would be very helpful if this was available on py2.x.

For every new feature, there is someone who thinks it would be helpful 
if it were availale in an earlier version. Backports of library features 
are sometimes available on PyPI, but this cannot be done for syntax 
features like 'nonlocal'.

'2.x' refers to a sequence of feature-frozen versions. It literally 
means '2.0 to 2.7', but may refer to '2.2 to 2.7' (because 2.2 gained 
new classes and iterators) or even a more restricted sequence. Core 
developers consider 3.2, or maybe a later version, to be the successor 
of 2.7.

-- 
Terry Jan Reedy