The super keyword is a reference variable that allows subclasses to access and invoke parent class methods and fields, providing subclasses with access to and invoke on parent classes’ methods and fields. It plays a critical role in Inheritance and Polymorphism by encouraging encapsulation and abstraction while permitting flexible code expansion.
Additionally, it plays an essential part in calling the constructor of its parent class from within a derived one.
Inheritance
Inheritance is one of the key concepts in object-oriented programming, enabling subclasses to inherit properties from their parent class without explicitly writing those properties down. Furthermore, inheritance makes code more maintainable by enabling developers to make changes directly on parent classes while seeing those changes propagate automatically down through all child classes.
Python’s super function provides the primary method for accessing methods from parent classes from child classes. Used within constructors to reference immediate parents, when called it returns a method object of that parent class whose methods are then called by child classes; providing an excellent example of inheritance and polymorphism at work in code.
Super is typically used in constructors; however, in situations of multiple inheritance its two argument form can play an even larger role. This is because child classes can specify both an immediate parent class and current object that cause super to perform method lookup according to order specified.
Multiple inheritance is one of the most prevalent types of inheritance in Python. This occurs when a child class inherits properties from multiple parent classes. Hierarchical and multilevel multiple inheritance are two of its most prevalent forms; an example would be when Person has a Child class called Employee that inherits some properties from it both directly or through parent classes like that Person had.
Polymorphism
Polymorphism refers to an object’s ability to take multiple forms. This enables different subclasses to implement methods differently; for instance, when Horse, Fish and Bird all descend from a base class called Animals they can each implement the Move function differently based on how their subclass descends; trotting might appear when running it on Horse class objects while swimming would cause fish swimming or flying would happen with Bird class objects using polymorphism as implementation of this function varies based on each subclass object’s implementation by all subclasses using polymorphism as its implementation by all subclasses using polymorphism.
Polymorphism and inheritance go hand-in-hand; an object that inherits from another superclass may override (replace) methods in its parent class, providing they use identical signatures in terms of name, parameter list and return type as its parent class method (this process is known as function overloading).
Runtime polymorphism or late binding is another method of overriding that works differently from compile-time overrides; it occurs when calls to overridden methods are resolved dynamically at run time rather than compile time. To implement runtime polymorphism in your program, the virtual keyword must be included and any argument checks or method calls will only occur at run time when your code executes, not compile time.
Accessing Parent Class Fields
Inheritance provides child classes with automatic access to the fields and methods of their parent class through inheritance. If the fields of the parent class are private – as they should be – child classes cannot directly access them using dot notation; rather they must access through either setting or getting methods instead. Luckily, parents can offer public accessors (also called getters) that enable child classes to retrieve field values as well as public modifiers (mutators/setters) that let their child classes modify them directly.
For accessing fields or data members in a parent class, child classes can use the super keyword. This will invoke its constructor, and make accessing its methods or fields possible. Failure to call its constructor first could prevent access from other child classes being possible.
Another significant aspect of the super keyword is that it must always be combined with this object in a derived class’s constructor. This is necessary because this object serves as a pointer to its parent class’s methods, and without passing one into its constructor, methods from this parent won’t work properly for its derived counterpart.
Calling Parent Class Methods
The super() method enables child classes to call a parent class’s methods from within their own code using its constructor or invoke its methods without overwriting any of them. By calling its methods using super() in child code, a parent method will still be invoked even if its implementation has changed by its child class parent.
As noted in the Introduction, Python is an object-oriented programming language. This means that classes can inherit from multiple base classes, and each class can contain its own methods and fields. Python’s super() function facilitates accessing parent class methods from child classes for easier polymorphism and code reuse.
Below is an example of an inheriting child class called d1 that inherits from its parent class p1. Within this d1 class is defined a method named first() that calls super() when invoked from within it, calling back into parent class p1’s method instead.
Super() also ensures that any future updates or bug fixes to p1’s method implementation benefit the d1 class automatically, helping maintain coherence and consistency across classes – one of the major draws of object-oriented programming for developers.