(Please note that most replies should trim at least one list from the Cc) On 3/23/07, guido.van.rossum <python-checkins@python.org> wrote:
Note: without the change to string.py, lots of spurious warnings happen. What's going on there?
I assume it was a defensive measure for subclasses of both Template and X, where X has its own metaclass (which might have an __init__ that shouldn't be ignored). This is where cooperative classes get ugly. You could argue that the "correct" code is to not bother making the super call if it would go all the way to object (or even type), but there isn't a good way to spell that.
+ # A super call makes no sense since type() doesn't define __init__(). + # (Or does it? And should type.__init__() accept three args?) + # super(_TemplateMetaclass, cls).__init__(name, bases, dct)
In this particular case, you could define a type.__init__ that did nothing. (If the signature were wrong, type.__new__ would have already caught it. If __new__ and __init__ are seeing something different, then the change was probably intentional.) The problem isn't really limited to type.__init__ though. You'll sometimes see similar patterns for __del__, close, save, etc. The main difference is that they have to either catch an error or check first, since object doesn't have an implementation of those methods. object.__init__ doesn't really do anything either, except check for errors. Getting rid of it should have the same effect as complaining about parameters. The ideal solution (discussion of which probably ought to stay on python-ideas) might be to replace object.__init__ with some sort of PlaceHolder object that raises an error *unless* called through a cooperative super. This PlaceHolder would also be useful for AbstractBaseClasses/Interfaces. PlaceHolder still wouldn't deal with the original concern of verifying that all arguments had already been stripped and used; but the ABCs might be able to. -jJ
Modified: python/trunk/Lib/string.py ============================================================================== --- python/trunk/Lib/string.py (original) +++ python/trunk/Lib/string.py Fri Mar 23 05:58:42 2007 @@ -108,7 +108,9 @@ """
def __init__(cls, name, bases, dct): - super(_TemplateMetaclass, cls).__init__(name, bases, dct) + # A super call makes no sense since type() doesn't define __init__(). + # (Or does it? And should type.__init__() accept three args?) + # super(_TemplateMetaclass, cls).__init__(name, bases, dct) if 'pattern' in dct: pattern = cls.pattern else: