[Python-Dev] Re: [XML-SIG] printing Unicode xml to StringIO

[Martin v. Loewis]

> Both of these implementation are targetted at providing
> a file IO like interface to in-memory "files". Since Python
> file object don't magically support Unicode, I wonder where the
> idea came from that StringIO/cStringIO should.

The exact source of this idea is unknown. However, there are many
early references to it:

- codecs.open returns an "encoded file" which "will only accept
  ... Unicode objects". That is perhaps the earliest precedent of
  a file object supporting Unicode.

- At some point in time, you said that it is a bug that cStringIO
  does not support Unicode strings, see
http://mail.python.org/pipermail/i18n-sig/2000-November/000550.html

- the documentation of StringIO suggests that they should accept
  Unicode.

So I would not blame the users for adopting far-off ideas, when the
Python core itself suggests that these ideas are Pythonic.

> That patch I applied to StringIO/cStringIO for 2.2 was
> aimed at making these two more compatible to the standard
> Python file object. The latter uses the "s#" parser
> marker for .write() and thus can also accept memory
> buffers. This was previously not possible with either
> of the two StringIO implementation (StringIO.py failed
> when trying to join different buffer compatible objects,
> cStringIO only accepted real string objects).

There is nothing wrong with that. The patch should just have
special-cased Unicode objects (and that bug can still be corrected).

Regards,
Martin