Inheritance Principle

Inheritance is a way of extending class. The new class (child class) builds logic on the top of the parent class (super class).

Here's an example:

class Vehicle:
    def representation(self):
        print(self.__make, self.__model)
            
    def getInsuranceCost(self, months):
        return 0
            
    def getMake(self):
        return self.__make
            
    def setMake(self, value):
        self.__make = value
            
    def getModel(self):
        return self.__model
            
    def setModel(self, value):
        self.__model = value
            
# Car inherits Vehicle:
class Car(Vehicle):
    # Overwriting method:
    def getInsuranceCost(self, months):
        return months * 25
            
    # Adding constructor:
    def __init__(self, makeValue, modelValue, doorsCountValue):
        self.setMake(makeValue)
        self.setModel(modelValue)
        self.setDoorsCount(doorsCountValue)
            
    # Method extension:
    def representation(self):
        super().representation()
        print("Doors count:", self.__doorsCount)
            
    # Adding new methods:
    def getDoorsCount(self):
        return self.__doorsCount
            
    def setDoorsCount(self, value):
        self.__doorsCount = value

car = Car("Toyota", "Corolla", 4)
            
# Method that was extended:
car.representation()
            
print("------")
# getter that was added:
print(car.getDoorsCount())
print("------")
            
# Methods that weren't changed:
print("Make: " + car.getMake())
print("Model: " + car.getModel())
print("------")
            
# Method that was overwritten:
print("Insurance cost:", car.getInsuranceCost(12), "$")

Output:

Basically the child class can add, extend, rewrite or use the inherited logic from the parent.

For this example:

Added logic:
- getter for doorsCount (line 38)
Extended logic:
- representation method (line 33)
Entirely rewritten logic:
- getInsuranceCost (line 23)
Not modified logic:
- getter for make (line 8)
- getter for model (line 14)
- setter for make (line 11)
- setter for model (line 17)