On Fri, Jan 2, 2009 at 11:10 AM, spir <denis.s...@free.fr> wrote: > Can someone explain the following? > > ============================ > class Type(object): > pass > o = Type() > o.a = 1 > print o, o.a > print dir(object) > ==> ['__class__', '__delattr__', '__doc__', '__getattribute__', '__hash__', > '__init__', '__new__', > '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__str__'] > ==> no problem > o = object() > o.a = 1 > ==> AttributeError: 'object' object has no attribute 'a' > ================================ > > Type does not create any additional attribute or member, or what? > Does this mean that the type 'object' has a hidden __slots__ attr? > Then why doesn't Type inherit it, like any attribute?
I'm no expert on this so take this with salt... IIUC the attributes of built-in objects are hard-coded in tables. The hard-coded tables don't include __dict__ attributes so you can't add attributes to instances of built-in types. This is similar to what __slots__ does for user-defined classes though the implementation is different. The special behaviour of a class with a __slots__ attribute only affects the class that defines __slots__, not subclasses. See http://docs.python.org/reference/datamodel.html#id3: "The action of a __slots__ declaration is limited to the class where it is defined. As a result, subclasses will have a __dict__ unless they also define __slots__." Kent _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
