[EMAIL PROTECTED] (Bengt Richter) writes: > On Thu, 07 Jul 2005 09:51:42 +0200, Thomas Heller <[EMAIL PROTECTED]> wrote: > >>[EMAIL PROTECTED] (Bengt Richter) writes: >> >>> On Wed, 06 Jul 2005 17:57:42 +0200, Thomas Heller <[EMAIL PROTECTED]> wrote: >>> >>>>I'm trying to implement __iter__ on an abstract base class while I don't >>>>know whether subclasses support that or not. >> >>> Will a property or custom descriptor do what you want? E.g. >>> >>> >>> class Base(object): >>> ... def __getIter(self): >>> ... if hasattr(self, "Iterator"): >>> ... return self.Iterator >>> ... raise AttributeError, name >>> ... __iter__ = property(__getIter) > [...] >> >>Yep, that's exactly what I need - thanks. >> > BTW, I forgot to mention that you could use property as a decorator > in the above single-argument case: > > >>> class Base(object): > ... @property > ... def __iter__(self): > ... if hasattr(self, "Iterator"): > ... return self.Iterator > ... raise AttributeError, name
Of course. I didn't spot this, but I cannot use this anyway for 2.3 compatibility. > ... > >>> class Concrete(Base): > ... def Iterator(self): > ... yield 1 > ... yield 2 > ... yield 3 > ... > >>> iter(Base()) > Traceback (most recent call last): > File "<stdin>", line 1, in ? > TypeError: iteration over non-sequence > >>> iter(Concrete()) > <generator object at 0x02EF152C> > >>> list(iter(Concrete())) > [1, 2, 3] > > Hope there isn't a gotcha for your use case in the way an instance attribute > of the same name is allowed. A custom descriptor could eliminate that. > > >>> inst = Concrete() > >>> list(iter(inst)) > [1, 2, 3] > >>> inst.__init__ = 'abc' > >>> list(iter(inst)) > [1, 2, 3] > >>> inst.__init__ > 'abc' I don't understand what you mean here. A __iter__ instance attribute? Thomas -- http://mail.python.org/mailman/listinfo/python-list
