Question

Look at the following code, which is the first line of a class definition. What is the name of the superclass? What is the name of the subclass? class Canary (Bird):

Short answer

Answer: The subclass is Canary, and the superclass is Bird.

Step-by-step solution

Identify the Class Definition

In the given code, there is a class definition with the syntax "class Canary (Bird):" which means we have a class named Canary inheriting from the class Bird.

Finding the Subclass

A subclass is a class that inherits from another class, also called the superclass. In our code, the "Canary" class is inheriting from the "Bird" class. Therefore, the name of the subclass is Canary.

Finding the Superclass

A superclass is a class that is inherited by other classes, also called the subclasses. In our code, the "Bird" class is the class being inherited by the "Canary" class. This makes the Bird class the superclass. So, the name of the superclass is Bird.

Key concepts

Class Definition

A class definition is a blueprint for creating objects in object-oriented programming. Think of it as a template that defines the properties and behaviors that the objects created from it will have. This is achieved using the `class` keyword in Python. For example,

• `class Canary (Bird):`

In this snippet, `Canary` is the name of the new class we are defining. It is important to ensure that class names are descriptive and begin with an uppercase letter to follow Python's naming conventions.
Classes can define their own methods and variables that are specific to the objects created from them. The defined class can then be instantiated to create individual objects having distinct data. To sum it up, when you define a class, you are establishing the framework for how an object should behave and what attributes it should have.

Inheritance in Python

Inheritance is a fundamental concept in object-oriented programming that allows a new class, known as a subclass, to take on the properties and methods of another class, known as a superclass. This is a powerful feature that promotes code reusability and hierarchical class organization. In Python, it is indicated by writing the name of the superclass in parentheses next to the new subclass name:

• `class Canary (Bird):`

Here, the `Canary` class inherits from the `Bird` class, meaning that `Canary` has access to the properties and methods of `Bird`. This eliminates the need to rewrite code, as it can simply inherit the behavior from the superclass.
Python allows single inheritance (inheritance from one superclass) and multiple inheritance (inheritance from multiple superclasses), providing flexibility in how classes can be structured. With inheritance, subclasses can override methods from the superclass, providing their own implementation where necessary, while still utilizing the existing functionality provided by the superclass.

Subclass and Superclass Identification

To identify the subclass and superclass in a class relationship, you simply need to understand which class is being inherited from and which one is doing the inheriting. Using the example `class Canary (Bird):`:

• The subclass is `Canary`, as it is the class that inherits the properties of another class.
• The superclass is `Bird`, as it is the class from which properties and methods are being inherited.

The subclass can be thought of as a specialized version of the superclass, often adding additional properties or methods, or modifying existing ones.
An effective way to remember which is which is: the **sub**class is asking the **super**class for its abilities. This relationship is fundamental in designing class hierarchies where each level of the hierarchy is a more specialized form than the one above it. As you build complex systems, identifying subclasses and superclasses accurately creates a solid foundation for your program structure.