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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: Flexible string representation, unicode, typography, ...
Date: Sun, 02 Sep 2012 22:33:55 -0400
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Xref: csiph.com comp.lang.python:28334

On 9/2/2012 9:54 PM, Steven D'Aprano wrote:
> On Sun, 02 Sep 2012 23:38:49 +0300, Serhiy Storchaka wrote:
>
>> On 30.08.12 09:55, Steven D'Aprano wrote:
>>> And Python's solution uses those: UCS-2, UCS-4, and UTF-8.
>>
>> I see that this misconception widely spread.
>
> I am not familiar enough with the C implementation to tell what Python
> 3.3 actually does, and the PEP assumes a fair amount of familiarity with
> the CPython source. So I welcome corrections.
>
>
>> In fact Python 3.3 uses four kinds of ready strings.
>>
>> * ASCII. All codes <= U+007F.
>> * UCS1. All codes <= U+00FF, at least one code > U+007F.
>> * UCS2. All codes <= U+FFFF, at least one code > U+00FF.
>> * UCS4. All codes <= U+0010FFFF, at least one code > U+FFFF.
>
> Where UCS1 is equivalent to Latin-1, correct?
>
> UCS2 is what Python 3.2 narrow builds uses for all strings, including
> codes > U+FFFF using surrogate pairs.
>
> UCS4 is what Python 3.2 wide builds uses for all strings.
>
> This means that Python 3.3 will no longer have surrogate pairs.

Basically, yes. I believe CPython will only use surrogate code points if 
one requests errors=surrogate-escape on decoding or explicitly puts them 
in a literal (\unnnn or \Ummmmmmmm). The consequences fall under the 
'consenting adults' policy.

-- 
Terry Jan Reedy