Study and understand this example and you’ll grasp most of what one needs to know about writing metaclasses.

To control the creation and initialization of the class in the metaclass, you can implement the metaclass’s __new__ method and/or __init__ constructor [6]. Most real-life metaclasses will probably override just one of them. __new__ should be implemented when you want to control the creation of a new object (class in our case), and __init__ should be implemented when you want to control the initialization of the new object after it has been created.