Creating a class (either using the 'class' statement or using type()) creates a circular reference.

I've attached a script that simply demonstrates this. The problem is caused by the fact that MyClass.__dict__['__dict__'].__objclass__ is MyClass.

Although most of the times classes are never deleted when the interpreted exits, some programs (like the popular Django framework) create temporary classes. And this is a pain because you can't disable the garbage collector.