How to Use Class Inheritance in Python

By Birtchum Thompson | April 4, 2020

Class inheritance is an important concept in Python and OOP languages in general. Inheritance’s main benefit is reusability, allowing the properties and methods of the parent class to be used by the child class.

We will start by creating our parent class, Vehicle. The Vehicle class’s constructor will accept 3 arguments: type, wheels, and engine. Wheels and engine are initialized as True since we can assume that all vehicle types we will deal with in this tutorial have both. The Vehicle class also has a single method that prints a sentence revealing the vehicle type.

class Vehicle:
    def __init__(self, type, wheels=True, engine=True):
        self.type = type
        self.wheels = wheels
        self.engine = engine

    def get_type(self):
        return f'This vehicle is a {self.type}'

Python

To test our Vehicle class, we create an instance and print each property, then call the get_type() method like this:

class Vehicle:
    def __init__(self, type, wheels=True, engine=True):
        self.type = type
        self.wheels = wheels
        self.engine = engine

    def get_type(self):
        return f'This vehicle is a {self.type}'


vehicle = Vehicle('train')
print(vehicle.type)
print(vehicle.wheels)
print(vehicle.engine)
print(vehicle.get_type())

Python

Then, run the application. The output prints the vehicle’s properties and vehicle type sentence as expected.

train
True
True
This vehicle is a train

Next, we remove our tests and create 2 child classes that will inherit from Vehicle: Car and Truck. For inheritance to work, Vehicle must be passed as an argument to both Car and Truck. The child classes also each accept 2 additional arguments: brand and color. We can initialize the vehicle types for our child classes since we know that they are car and truck, respectively. Our child class constructor will assign brand and color as object attributes, but the super() function must be used to finish initialization with the parent class to be able to access its properties and methods.

class Vehicle:
    def __init__(self, type, wheels=True, engine=True):
        self.type = type
        self.wheels = wheels
        self.engine = engine

    def get_type(self):
        return f'This vehicle is a {self.type}'


class Car(Vehicle):
    def __init__(self, brand, color, type='car'):
        self.brand = brand
        self.color = color
        super().__init__(type)


class Truck(Vehicle):
    def __init__(self, brand, color, type='truck'):
        self.brand = brand
        self.color = color
        super().__init__(type)

Python

Let’s test the application by creating instances of both car and truck, then printing out all of their properties and their get_type() method.

class Vehicle:
    def __init__(self, type, wheels=True, engine=True):
        self.type = type
        self.wheels = wheels
        self.engine = engine

    def get_type(self):
        return f'This vehicle is a {self.type}'


class Car(Vehicle):
    def __init__(self, brand, color, type='car'):
        self.brand = brand
        self.color = color
        super().__init__(type)


class Truck(Vehicle):
    def __init__(self, brand, color, type='truck'):
        self.brand = brand
        self.color = color
        super().__init__(type)


truck = Truck('Dodge', 'red')
print(truck.brand)
print(truck.color)
print(truck.type)
print(truck.wheels)
print(truck.get_type())

car = Car('Chevy', 'blue')
print(car.brand)
print(car.color)
print(car.type)
print(car.wheels)
print(car.get_type()

Python

After running the application, we see that our child classes did, indeed, inherit the properties and method of their parent class.

Dodge
red
truck
True
This vehicle is a truck
Chevy
blue
car
True
This vehicle is a car

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