[Python-Dev] Decoding incomplete unicode (original) (raw)

M.-A. Lemburg mal at egenix.com
Thu Aug 19 18:06:46 CEST 2004

Walter Dörwald wrote:

Martin v. Löwis wrote:

Walter Dörwald wrote:

They will not, because StreamReader.decode() already is a feed style API (but with state amnesia).

Any stream decoder that I can think of can be (and most are) implemented by overwriting decode(). I consider that an unfortunate implementation artefact. You either use the stateless encode/decode that you get from codecs.get(encoder/decoder) or you use the file API on the streams. You never ever use encode/decode on streams. That is exactly the problem with the current API. StreamReader mixes two concepts: 1) The stateful API, which allows decoding a byte input in chunk and the state of the decoder is kept between calls. 2) A file API where the chunks to be decoded are read from a byte stream. I would have preferred if the default .write implementation would have called self.internalencode, and the Writer would contain a Codec, rather than inheriting from Codec. This would separate the two concepts from above.

Note that StreamCodec only inherits from Codec for convenience reasons (you can define a StreamCodec using the stateless .encode() and .decode() methods you get from Codec) and for logical reasons: a StreamCodec happens to be a Codec as well, so isinstance(obj, Codec) should be true for a StreamCodec as well.

There's nothing preventing you from overriding .encode() and .decode() in a StreamReader or adding new methods that implement a different approach to encode and decode.

Users should always use the file API of StreamReader et al., not the .encode() and .decode() methods.

-- Marc-Andre Lemburg eGenix.com

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