Thomas Heller <[EMAIL PROTECTED]> writes on Wed, 06 Jul 2005 18:07:10 +0200: > Thomas Heller <[EMAIL PROTECTED]> writes: > ... > > class Base: > > def __getattr__(self, name): > > if name == "__iter__" and hasattr(self, "Iterator"): > > return self.Iterator > > raise AttributeError, name > > > > class Concrete(Base): > > def Iterator(self): > > yield 1 > ... > > If, however, I make Base a newstyle class, this will not work any > > longer. __getattr__ is never called for "__iter__" (neither is > > __getattribute__, btw). Probably this has to do with data descriptors > > and non-data descriptors, but I'm too tired at the moment to think > > further about this. > > > > Is there any way I could make the above code work with new style > > classes? > > I forgot to mention this: The Base class also implements a __getitem__ > method which should be used for iteration if the .Iterator method in the > subclass is not available. So it seems impossible to raise an exception > in the __iter__ method if .Iterator is not found - __iter__ MUST return > an iterator if present.
Then, it should return an interator (a new object) that uses the "__getitem__" method to iterate. Dieter -- http://mail.python.org/mailman/listinfo/python-list
