I was trying to inherit xrange (to implement membership testing with in, as well as iteration). But I got the following error message:
TypeError: Error when calling the metaclass bases
type 'xrange' is not an acceptable base type
What's special about xrange?
xrange is implemented in C. As you can see in Tim Peters' post, there should be a convincing use case in order to justify the extra effort needed to allow subclassing of it.