Perhaps this is more approprate for python-list but I looks like a bug to me. Example code:
class A: def __str__(self): return u'\u1234'
'%s' % u'\u1234' # this works '%s' % A() # this doesn't work
It will work if 'A' subclasses from 'unicode' but should not be necessary, IMHO.
You know better than to say "doesn't work". I assume you mean the latter raises UnicodeEncodeError.
Any reason why this shouldn't be fixed?
Didn't we just go thru this, last week or so? PyObject_Str() never returns a unicode (it returns a str). That is, str(A()) raises UnicodeEncodeError, and that's out of interpolation's hands. As Martin said last time, a __str__ method that returns a unicode doesn't make much sense.
I'm not sure you really mean "it will work if 'A' subclasses from 'unicode'" either:
... def __str__(self): ... return u'\u1234' ...
'%s' % A()
That is, A.__str__ is ignored if A subclasses from Unicode. So "doesn't blow up" seems more on-target than "works" -- I don't think you expected an empty Unicode string here.