A metaclass is a Python feature that is considered by many as one of the most difficult things to understand in the language and is thus avoided by a great number of developers. In reality, it is not as complicated as it sounds once you understand a few basic concepts. As a reward, knowing how to use metaclasses grants you the ability to do things that are not possible without them.
A metaclass is a type (class) that defines other types (classes). The most important thing to know in order to understand how they work is that classes (so, types that define object structure and behavior) are objects too. So, if they are objects, then they have an associated class. The basic type of every class definition is simply the built-in
type class (see Figure 8.1).
Figure 8.1: How classes are typed
In Python, it is possible to substitute the metaclass for a class object with your own type. Usually, the new metaclass is still the subclass of the
type metaclass (refer...