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

Nick Coghlan ncoghlan at gmail.com
Fri Nov 15 00:11:02 CET 2013

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 > rot13 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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