I do not mean to reopen the bug (there are supposedly much more important things to work on in Python). 

But just for the record, let me state that I feel like there is some misleading inconsistency here:

- by definition, a new style class is "Any class which inherits from object" ( see http://docs.python.org/glossary.html#term-new-style-class ) ;

- to support this statement, new classes are indeed explicitly defined in the form "NewClass(object)" ;

- now isinstance(), that is supposed to "return whether an object is an instance of a class or of a subclass thereof" (see help(isinstance)), returns True for old-style objects.

It also seems reasonable if the descendants of a class will inherit its powers, which -- in the case of the old-style classes -- they obviously don't.

Furthermore, I personally see no /point/ in returning True for isinstance(Old(), object): as it is quite misleading, one could easily have made it returning e.g. None as well.

As I completely accept the fact it's a feature -- ( may be slightly confusing, and probably also useless -- but ... hey, nobody's perfect ) -- should I take then calling

issubclass(obj.__class__, object) 

to be the official way to distinguish between the new-style and the old-style classes?