Inheritance

Inheritance

Process of acquiring properties from one class to another classes. Create hierarchy between classes.

Hierarchy flow:

Coding example:

Parent class.

class Animal:
    weight: int
    color: str
    age: int
    animal_type: str

    def eat(self):
        print('Animal eating')

    def sleep(self):
        print('Animal sleeping')

Child class:

class Dog(Animal):
 # All animal attributes are inherited.
    can_shed: bool
    domestic_name: str
#All animal methods are inherited.


Accessing through child class instance parent class methods.
dog = Dog()
dog.eat()

It will provide the result as child has inherited all public attributes and methods of parent class.

Adding child specific function to child class.

class Dog(Animal):
 # All animal attributes are inherited.
    can_shed: bool
    domestic_name: str

    def talk(self):
        print("Bark!")
#All animal methods are inherited.

dog = Dog()
dog.talk() -> it will provide result as talk is child method and child instance has access to it.


animal = Animal()
animal.talk() -> it will not execute and will provide error as it is a child class method and parent don't have any means to know about it.

What is method override?

If we have a method in parent class and child class inherited it and modified it's definition at it's class then that use of method is own as overriding.

Example:
class Animal:
    weight: int
    color: str
    age: int
    animal_type: str

    def eat(self):
        print('Animal eating')

    def sleep(self):
        print('Animal sleeping')

class Dog(Animal):
 # All animal attributes are inherited.
    can_shed: bool
    domestic_name: str

    def talk(self):
        print("Bark!")
    
    def eat(self):
        print('Chews bone!")

dog=Dog()
dog.eat() - > It will print the information from child class as child class has already overridden parent class method eat().

dog.sleep() -> It will check first child class for method when it won't find then will search in parent class and will print its result.

Code from IDE:

Scenario want to implement inheritance in our arena game:
  • Currently our only class is Enemy()
    • Enemy() is our parent class
  • We will now create two children classes
    • Zombie()
    • Ogre()

Enemy class:
# Parent class Enemy is also known as super class or base class.

class Enemy:

    def __init__(self, typeOfEnemy: str,
                 healthPoints: int = 10,
                 attack_damage: int = 1):
        self.__typeOfEnemy = typeOfEnemy
        self.healthPoints = healthPoints
        self.attack_damage = attack_damage

    def get_typeOfEnemy(self):
        return self.__typeOfEnemy
   
    def talk(self):
        print(f"I am a {self.__typeOfEnemy}. Be prepared to fight!")

    def walk_forward(self):
        print(f"{self.__typeOfEnemy} moves closer to you!")

   


Zombie class:
# Child class of Enemy Zombie
from Enemy import Enemy

class Zombie(Enemy):
    def __init__(self, healthPoints, attack_damage):
        super().__init__(typeOfEnemy='Zombie', healthPoints=healthPoints,
                         attack_damage=attack_damage)
        self.healthPoints = healthPoints
        self.attack_damage = attack_damage

    # method overriding
    # This method is overriding the talk method of parent class Enemy
    def talk(self):
        print(f"Zombie: Braaaains!")

    #  new method specific to Zombie class
    def spread_diesease(self):
        print(f"Zombie: Spreading disease!")

Ogre class:
# Child class of Enemy Ogre
from Enemy import Enemy

class Orge(Enemy):
    def __init__(self, healthPoints, attack_damage):
        super().__init__(typeOfEnemy='Ogre', healthPoints=healthPoints,
                         attack_damage=attack_damage)
        self.healthPoints = healthPoints
        self.attack_damage = attack_damage

    # method overriding
    # This method is overriding the talk method of parent class Enemy
    def talk(self):
        print(f"Ogre: Smash them!")

main.py

# using implementation
from Enemy import Enemy
from Zombie import Zombie
from Ogre import Orge

zombie=Zombie(healthPoints=15, attack_damage=3)

# This will call the getter method for typeOfEnemy
print(f"Enemy type = {zombie.get_typeOfEnemy()}")

# This will call the talk method from the Zombie class
print(f"{zombie.talk()}")

# This will call the spread_diesease method from the Zombie class
print(f"{zombie.spread_diesease()}")

ogre=Orge(healthPoints=25, attack_damage=7)

# This will call the getter method for typeOfEnemy
print(f"Enemy type = {ogre.get_typeOfEnemy()}")

# This will call the talk method from the Ogre class
print(f"{ogre.talk()}")

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