(I'm posting to python-dev, because this isn't strictly 3.0 related. Hopefully most people read it in addition to python-3000).
I'm working on backporting the changes I made for PEP 3101 (Advanced String Formatting) to the trunk, in order to meet the pre-PyCon release date for 2.6a1.
I have a few questions about how I should handle str/unicode. 3.0 was pretty easy, because everything was unicode.
1: How should the builtin format() work? It takes 2 parameters, an object o and a string s, and returns o.__format__(s). If s is None, it returns o.__format__(empty_string). In 3.0, the empty string is of course unicode. For 2.6, should I use u'' or ''?
2: In 3.0, object.__format__() is essentially this:
class object: def __format__(self, format_spec): return format(str(self), format_spec)
In 2.6, I assume it should be the equivalent of:
class object: def __format__(self, format_spec): if isinstance(format_spec, str): return format(str(self), format_spec) elif isinstance(format_spec, unicode): return format(unicode(self), format_spec) else: error
Does that seem right?
3: Every overridden __format__() method is going to have to check for string or unicode, just like object.__format() does, and return either a string or unicode object, appropriately. I don't see any way around this, but I'd like to hear any thoughts. I guess there aren't all that many __format__ methods that will be implemented, so this might not be a big burden. I'll of course implement the built in ones.
Thanks in advance for any insights.