Class and Class Inheritance Syntax in Python

Table of Contents

Class in Python
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A class is the cornerstone of Object-Oriented Programming (OOP). The concept of “object-oriented” means abstracting real-world entities into objects in code, and a class serves as the blueprint to define these objects. This might sound abstract—here’s an example: a dog is a class with attributes like name and age, while a specific dog like Xiao Hei is an object that has its own name and age. Below is the syntax for defining classes in Python:

# 1. Define a class
class Dog:
    def __init__(self, name, age):
        self.name = name  # attribute
        self.age = age

    def bark(self):  # method
        print(f"{self.name}: Woof!")

# 2. Create an object
my_dog = Dog("Xiao Hei", 3)

# 3. Use the object
print(my_dog.name)  # access attribute
my_dog.bark()       # call method

Class inheritance in Python
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To better follow the DRY (Don’t Repeat Yourself) principle and reduce repetitive code, classes can use inheritance. Inheritance means that a “child class” can inherit the attributes and methods from a “parent class”. For example, both “cat” and “dog” are types of “animals”. They both eat, but make different sounds. So we can first write an Animal class that contains the eat method, and then let both Cat and Dog inherit from it. The syntax in Python is as follows:

class Animal:
    def __init__(self, name):
        self.name = name

    def eat(self):
        print(f"{self.name} is eating")

    def speak(self):
        print(f"{self.name} made a sound")

class Dog(Animal):
    def __init__(self, name, breed):
        # Call the parent's __init__ method to set name
        super().__init__(name)
        self.breed = breed
        print(f"Dog: Breed is {self.breed}")

    def speak(self):
        super().speak()  # Optional: call parent's speak
        print(f"{self.name}: Woof!")


class Cat(Animal):
    def __init__(self, name, color):
        super().__init__(name)
        self.color = color
        print(f"Cat: Color is {self.color}")

    def speak(self):
        print(f"{self.name}: Meow~")
        
# Example usage
dog = Dog("Xiao Hei", "Labrador")
cat = Cat("Xiao Hua", "White")

dog.eat()
dog.speak()

cat.eat()
cat.speak()