Neil Schemenauer wrote:
On Wed, Mar 09, 2005 at 11:10:59AM +0100, M.-A. Lemburg wrote:
The patch implements the PyObjbect_Text() idea (an API that
returns a basestring instance, ie. string or unicode) and
then uses this in '%s' (the string version) to properly propogate
to u'%s' (the unicode version).
Maybe we should also expose the C API as suggested in the patch,
e.g. as text(obj).
Perhaps the right thing to do is introduce a new format code that
means insert text(obj) instead of str(obj), e.g %t. If we do that
though then we should make '%s' % u'xyz' return a string instead of
a unicode object. I suspect that would break a lot of code.
It would result in lots of UnicodeErrors due to failing
conversion of the Unicode string to a string. Plus it
would break with the general rule of always coercing to
Unicode (see below) and lose us the ability to write
polymorphic code.
OTOH, having %s mean text(obj) instead of str(obj) may work just
fine. People who want it to mean str() generally don't have any
unicode strings floating around so text() has the same effect.
People who are using unicode probably would find text() to be more
useful behavior. I think that's why someone hacked PyString_Format
to sometimes return unicode strings.
That wasn't a hack: it's part of the Unicode integration logic
which always coerces to Unicode if strings and Unicode meet. In
the above case a string format string meets a Unicode object as
argument which then results in a Unicode object to be returned.
Regarding the use of __str__, to return a unicode object: we could
introduce a new slot (e.g. __text__) instead. However, I can't see
any advantage to that. If someone really wants a str object then
they call str() or PyObject_Str().
Right.
--
Marc-Andre Lemburg
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