At a rather abstract level,
super () provides access to those methods of the superclass (parent class) that have been overridden in the subclass (child class) that inherits from it. Consider the example code below, here we have a class named
Square and another class named
Cube which inherits from
Square . P >
Note: Since the
Cube class does not have a
__init __ () method, the
__init __ () from the
Square class will be used to initialize
Cube instances (the main inheritance property).
Looking at this example, we know that each face of the cube is a square, and therefore the
face_area Cube represents the
area of the square. Now it makes sense to evaluate
face_area using the
area () method of the
Square class rather than calculating it manually, this will not only save us from rewriting the code, but also will allow you to change the logic of the
area () from one place. But since we have overridden the
area () method in
Cube , we cannot call the
area () method on
self.area () .
Now, this is a situation where
super() comes to the rescue.
super () returns the proxy object of the parent class and then you call a method of your choice on that proxy object, this way we can call the
area () method
Square class using
super () as
super().area() Here follows the modified definition of
class Cube .
Note that we could have named
Square.area () and not
super (). area ()
Square.area () , but it`s easier for the last creator to change the superclass or rename it as needed, making the code much easier to maintain.
Passing Arguments to
super () —
In the previous section, we discussed how to use
super () without any either parameters, but this only gives us access to the methods of this soup of the class that is the immediate parent of the subclass.
To access the methods of this superclass, which is not the immediate parent of the subclass, we use
super () with two arguments. Let`s look at an example of three classes named
Cube to understand how to use
super () with arguments ...
Now the cube — it is simply a special type of square prism whose height is equal to the side of its base, and therefore the cube resembles a square prism much more than a square. Therefore, in this example,
class Cube will inherit
class SquarePrism and
class will inherit
class Square . For the
Square class, we will use the same definition that we used in the previous section. Below is the definition of our newly defined
SquarePrism has two attributes: the side of its square base and the height of the square prism. The
face_area () instance method returns a tuple of two numbers representing the base area of the square prism and the side area of the square prism. Since the base is a square, for the base area of a square prism, we name the
Square.area () method as
super (). Area ()
super (). area () . The
area () method returns the total surface area of the square prism.
So far we have used
super () without any parameters, now a new one follows. a
Cube class that will demonstrate using
super () with parameters.
__init __ () and
area () methods, the
Cube method is slightly different from its counterpart
SquarePrism.face_are a () . For a cube, the side area is equal to the base area and therefore it makes no sense for
face_area () to return a tuple, so
class Cube will return the area one of the faces of the cube. ,
Now, since each face of the cube is a square, it makes sense again to use the
class Square method. Now, since
class Square is not the immediate parent of
class Cube , we cannot access the
class Square as
super (). area ()
SquarePrism.area () it will instead call
SquarePrism.area () . p>
Here we use
super (SquarePrism, self) .face_area () to call the
class Square method . In the first argument,
SquarePrism means that
super () looks for the
area () method in the immediate parent of the
SquarePrism class which located in
class Square . Using
self as the second parameter provides the context of the current
Cube object for
super () for the requested
area () method.
Remember that using
super () in a two-argument form requires that the object passed as the second argument be an instance of the
type passed to as the first argument.
Note: Because the
Cube class is a child of the
class SquarePrism , the
Cube instance is also an instance of
class SquarePrism and
class Square .
Try the following code snippet and view the output to clarify the above point.
It`s worth noting that the
super () with a null argument can only be used inside the class definition, since it is automatically filled in by the compiler with the appropriate parameters, i.e. if we using
super () inside a class say
super () will be converted to
super (X, self) code > the compiler.
Although the null-argument
super () form is popular with developers, the two-argument form is not very useful. But in multiple inheritance, the two-argument form plays a very important role.