[Python-Dev] str object going in Py3K (original) (raw)

M.-A. Lemburg mal at egenix.com
Fri Feb 17 14:10:43 CET 2006

Walter Dörwald wrote:

Guido van Rossum wrote:

On 2/16/06, M.-A. Lemburg <mal at egenix.com> wrote: What will be the explicit way to open a file in bytes mode and in text mode (I for one would like to move away from open() completely as well) ?

Will we have a single file type with two different modes or two different types ? I'm currently thinking of an I/O stack somewhat like Java's. At the bottom there's a class that lets you do raw unbuffered reads and writes (and seek/tell) on binary files using bytes arrays. We can layer onto this buffering, text encoding/decoding, and more. (Windows CRLF<->LF conversion is also an encoding of sorts). Years ago I wrote a prototype; checkout sandbox/sio/. However sio.DecodingInputFilter and sio.EncodingOutputFilter don't work for encodings that need state (e.g. when reading/writing UTF-16). Switching to stateful encoders/decoders isn't so easy, because the stateful codecs require a stream-API, which brings in a whole bunch of other functionality (readline() etc.), which we'd probably like to keep separate. I have a patch (http://bugs.python.org/1101097) that should fix this problem (at least for all codecs derived from codecs.StreamReader/codecs.StreamWriter). Additionally it would make stateful codecs more useful in the context for iterators/generators. I'd like this patch to go into 2.5.

The patch as-is won't go into 2.5. It's simply the wrong approach: StreamReaders and -Writers work on streams (hence the name). It doesn't make sense adding functionality to side-step this behavior, since it undermines the design.

Like I suggested in the patch discussion, such functionality could be factored out of the implementations of StreamReaders/Writers and put into new StatefulEncoder/Decoder classes, the objects of which then get used by StreamReader/Writer.

In addition to that we could extend the codec registry to also maintain slots for the stateful encoders and decoders, if needed.

-- Marc-Andre Lemburg eGenix.com

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