I was working on writing the same thing, though less clearly. :) As a minor note, in Python 2, types.ClassType was a "thing": >>> import types >>> types.C

I was working on writing the same thing, though less clearly. :) As a minor note, in Python 2, types.ClassType was a "thing": >>> import types >>> types.ClassType is type False >>> isinstance(types.ClassType, type) True >>> my_class = types.ClassType("spam", bases=(), dict={}) >>> my_class <class __main__.spam at 0x106732670> I don't remember the details any more, but it looks like it was the base for class for old-style classes. Using your class definitions: >>> isinstance(OldStyleClass, types.ClassType) True >>> isinstance(NewStyleClass, types.ClassType) False Python 3 replaced that functionality with types.new_class(), which returns an instance of type 'type': >>> my_class = types.new_class("spam") >>> isinstance(my_class, type) True >>> my_class <class 'types.spam'> >>> type(my_class) <class 'type'> As I recall, in the early 1.x days it wasn't apparent that the class/type dichotomy was a problem. It took a lot of work during the 2.x era to bring them together.