[Python-Dev] Add transform() and untranform() methods

[Nick Coghlan]

On 15 Nov 2013 08:42, "Victor Stinner" <victor.stinner at gmail.com> wrote:
>
> Oh, I forgot to mention that I sent this email in reaction to this issue:
>
> http://bugs.python.org/issue19585
>
> Modifying the critical PyFrameObject because the codecs API raises
> surprising errors doesn't sound correct. I prefer to fix how codecs
> are used, than modifying the PyFrameObject.
>
> For more information, see the issue #7475 which a long history (4
> years) and many messages. Martin von Loewis wrote "I would still be
> opposed to such a change, and I think it needs a PEP." and I still
> agree with him on this point. Because they are different opinions and
> no consensus, a PEP is required to explain why we took this decision
> and list rejected alternatives.
>
> http://bugs.python.org/issue7475

Martin wrote that before it was pointed out there were existing functions
to handle the problem (I was asking for a PEP back then, too).

I posted my plan for dealing with this months ago without receiving any
complaints, and I'm annoyed you waited until I had actually followed
through and implemented it to complain about it and ask for Python 3's
binary codec support to stay broken instead :P

(Starting a new thread instead of replying to the one where I specifically
asked about taking the next step does nothing to improve my mood)

Regards,
Nick.

>
> Victor
>
> 2013/11/14 Victor Stinner <victor.stinner at gmail.com>:
> > Hi,
> >
> > I saw that Nick Coghlan documented codecs.encode() and
> > codecs.decode(), and changed the exception raised when codecs like
> > rot_13 are used on bytes.decode() and str.encode().
> >
> > I don't like the functions codecs.encode() and codecs.decode() because
> > the type of the result depends on the encoding (second parameter). We
> > try to avoid this in Python.
> >
> > I would prefer to split the registry of codecs to have 3 registries:
> >
> > - "encoding" (a better name can found): encode str=>bytes, decode
bytes=>str
> > - bytes: encode bytes=>bytes, decode bytes=>bytes
> > - str:  encode str=>str, decode str=>str
> >
> > And add transform() and untransform() methods to bytes and str types.
> > In practice, it might be same codecs registry for all codecs just with
> > a new attribute.
> >
> > Examples:
> >
> > - utf8: encoding
> > - zlib: bytes
> > - rot13: str
> >
> > The result type of bytes.transform/untransform would be bytes, and the
> > result type of str.transform/untransform would be str.
> >
> > I don't know which exception should be raised when a codec is used in
> > the wrong method. LookupError? TypeError "codec xxx cannot be used
> > with method xxx.xx"? Something else?
> >
> > codecs.encode/decode() documentation should be removed. The functions
> > should be kept, just in case if someone uses them.
> >
> > Victor
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