[Python-3000] PEP 3138- String representation in Python 3000

[M.-A. Lemburg]

On 2008-05-15 13:01, Nick Coghlan wrote:
> M.-A. Lemburg wrote:
>> I'll write up a PEP once we have a better understanding of the
>> details, e.g. of how the codec type information should be
>> defined...
>>
>> Here's a straight-forward approach:
>>
>> codecinfo.encode_type_combinations = [(bytes, bytes), (str, str)]
>> codecinfo.decode_type_combinations = [(bytes, bytes), (str, str)]
>>
>> for most codecs (e.g. utf-8, latin-1, cp850, etc.) this would
>> then be:
>>
>> codecinfo.encode_type_combinations = [(str, bytes)]
>> codecinfo.decode_type_combinations = [(bytes, str)]
> 
> Do we need something that flexible? Would a simpler approach with 
> separate "binary_transform" and "text_transform" flags be enough?
> 
> With the latter approach, the encode()/decode() methods could complain 
> if either of the transform flags was set on the codec, while the 
> transform()/untransform() methods could complain if the appropriate 
> transform flag *wasn't* set.

The above is a mechanism for codecs which do have a very
flexible interface in terms of supported types.

The methods on various objects are just convenience helpers
for easier access and in Py3k also provide type-safety.

The .transform() methods would simply check for the corresponding
type combination, ie. str.transform() would check for (str, str).
str.encode() would check for (str, bytes), bytes.decode() for
(bytes, str).

Alternatively, we could just not check the type combinations
at all and only apply the result type check.

> Note also that both bytearray and bytes provide decode() methods, and 
> will presumably provide transform() methods, so actual type annotations 
> may not be the best way to go about this.

I'm not sure I understand.

-- 
Marc-Andre Lemburg
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