[I18n-sig] Unicode experience

[Guido van Rossum]

> Toby Dickenson wrote:
> > 
> > I'm just nearing the end of getting Zope to play well with unicode
> > data. Most of the changes involved replacing a call to str, in
> > situations where either a unicode or narrow string would be
> > acceptable.
> > 
> > My best alternative is:
> > 
> > def convert_to_something_stringlike(x):
> >     if type(x)==type(u''):
> >         return x
> >     else:
> >         return str(x)
> > 
> > This seems like a fundamental operation - would it be worth having
> > something similar in the standard library?

Marc-Andre Lemburg replied:

> You mean: for Unicode return Unicode and for everything else
> return strings ?
> 
> It doesn't fit well with the builtins str() and unicode(). I'd
> say, make this a userland helper.

I think this would be helpful to have in the std library.  Note that
in JPython, you'd already use str() for this, and in Python 3000 this
may also be the case.  At some point in the design discussion for the
current Unicode support we also thought that we wanted str() to do
this (i.e. allow 8-bit and Unicode string returns), until we realized
that there were too many places that would be very unhappy if str()
returned a Unicode string!

The problem is similar to a situation you have with numbers: sometimes
you want a coercion that converts everything to float except it should
leave complex numbers complex.  In other words it coerces up to float
but it never coerces down to float.  Luckily you can write that as
"x+0.0" while converts int and long to float with the same value while
leaving complex alone.

For strings there is no compact notation like "+0.0" if you want to
convert to string or Unicode -- adding "" might work in Perl, but not
in Python.

I propose ustr(x) with the semantics given by Toby.  Class support (an
__ustr__ method, with fallbacks on __str__ and __unicode__) would also
be handy.

> BTW, could you elaborate a bit on your experience with adding
> Unicode support to Zope ? Such a report would certainly make
> a nice complement to the Unicode tutorial and help other
> people adding Unicode support to their apps.

Yes, that's what we need.  Thanks to Toby for pioneering this!

--Guido van Rossum (home page: http://dinsdale.python.org/~guido/)