[Python-Dev] bytes.from_hex() (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Sun Feb 19 19:55:49 CET 2006

Stephen J. Turnbull wrote:

BTW, what use cases do you have in mind for Unicode -> Unicode decoding?

I think "rot13" falls into that category: it is a transformation on text, not on bytes.

For other "odd" cases: "base64" goes Unicode->bytes in the decode direction, not in the encode direction. Some may argue that base64 is bytes, not text, but in many applications, you can combine base64 (or uuencode) with abitrary other text in a single stream. Of course, it could be required that you go u.encode("ascii").decode("base64").

def encode-mime-body (string, codec-list): if codec-list[0] not in charset-codec-list: raise NotCharsetCodecException if len (codec-list) > 1 and codec-list[-1] not in transfer-codec-list: raise NotTransferCodecException for codec in codec-list: string = string.encode (codec) return string

mime-body = encode-mime-body ("This is a pen.", [ 'shiftjis', 'zip', 'base64' ])

I think this is an example where you should use the codec API, as designed. As that apparently requires streams for stacking (ie. no support for codec stacking), you would have to write

def encode_mime_body(string, codec_list): stack = output = cStringIO.StringIO() for codec in reversed(codec_list): stack = codecs.getwriter(codec)(stack) stack.write(string) stack.reset() return output.getValue()

Notice that you have to start the stacking with the last codec, and you have to keep a reference to the StringIO object where the actual bytes end up.

Regards, Martin

P.S. there shows some LISP through in your Python code :-)

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