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Note that, so far, the metaclass inheritance chain exactly follows that of the class inheritance chain. But the metaclass chain extends further because Object class is the subclass of Class. All metaclasses are subclasses of Class. In early Smalltalks, there was only one metaclass called Class.
In knowledge representation, particularly in the Semantic Web, a metaclass is a class whose instances can themselves be classes. Similar to their role in programming languages, metaclasses in ontology languages can have properties otherwise applicable only to individuals, while retaining the same class's ability to be classified in a concept hierarchy.
In Python, everything is an object, even classes. Classes, as objects, have a class, which is known as their metaclass. Python also supports multiple inheritance and mixins. The language supports extensive introspection of types and classes. Types can be read and compared—types are instances of type. The attributes of an object can be ...
Not all languages support multiple inheritance. For example, Java allows a class to implement multiple interfaces, but only inherit from one class. [22] If multiple inheritance is allowed, the hierarchy is a directed acyclic graph (or DAG for short), otherwise it is a tree. The hierarchy has classes as nodes and inheritance relationships as links.
In class-based programming, inheritance is done by defining new classes as extensions of existing classes: the existing class is the parent class and the new class is the child class. If a child class has only one parent class, this is known as single inheritance , while if a child class can have more than one parent class, this is known as ...
In object-oriented programming, a class is a template that defines the state and behavior common to objects of a certain kind. A class can be defined in terms of other classes. [1] The concept of class hierarchy in computer science is very similar to taxonomy, the classifications of species.
The class A serves as a base class for the derived class B, which in turn serves as a base class for the derived class C. The class B is known as intermediate base class because it provides a link for the inheritance between A and C. The chain ABC is known as inheritance path. A derived class with multilevel inheritance is declared as follows:
The following python code establishes an explicit inheritance relationship between classes B and A, where B is both a subclass and a subtype of A, and can be used as an A wherever a B is required. class A : def do_something_a_like ( self ): pass class B ( A ): def do_something_b_like ( self ): pass def use_an_a ( some_a ): some_a . do_something ...