[EMAIL PROTECTED] wrote: > class Foo(object): > def __len__(): return 2 > __len__ = staticmethod(__len__) > print len(Foo) > >>> > Traceback (most recent call last): > File "C:/Dokumente und Einstellungen/All Users/Dokumente/foo.py", > line 4, in ? > print len(Foo) > TypeError: len() of unsized object > > However, the following works: > > class FooType(type): > def __len__(self): return self.l() > class Foo(object): > __metaclass__ = FooType > def l(): return 3 > l = staticmethod(l) > print len(Foo) > >>> > 3 > > Any good reason why the lookup process doesn't find __len__ as > staticmethod of the class?
Special methods of newstyle objects are always looked up in the class, and the class of a class is its metaclass. Therefore len(Foo()) invokes type(Foo()).__len__ which is the same as Foo.__len__ and len(Foo) invokes type(Foo).__len__ which (in your example) is the same as FooType.__len__. Peter -- http://mail.python.org/mailman/listinfo/python-list
