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Multi-Level Inheritance

Explore multi-level inheritance in Python by understanding how classes inherit from parent classes in a chain. Learn to implement inheritance hierarchies, override methods, and access superclass methods, building a foundational grasp of class behavior.

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Introduction

In addition to single-level inheritance, Python also supports multi-level inheritance. This means that you can create a hierarchy of classes, each inheriting from its superclass. The following figure illustrates an example of multi-level inheritance.

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The following hierarchy is clear from the above figure:

Class Superclass Relation
Carnivore Mammal Carnivore is a Mammal
Mammal Animal Mammal is an Animal
Animal - -

Implementation

Syntactically, multi-level inheritance in Python is quite similar to single-level inheritance. Consider the following basic code snippet:

Python 3.10.4
class Animal ():
  def __init__(self, name, food, characteristic): # Animal's constructor
    self.name = name # Animal's attribute
    self.characteristic = characteristic # Animal's attribute
    self.food = food # Animal's attribute
    print ("I am a " + str(self.name) + ".")
    
class Mammal (Animal): # Mammal inherits from Animal
  def __init__(self, name, food): # Mammal's constructor
    Animal.__init__(self, name, food, "warm blooded") # Animal's constructor
    print ("I am warm blooded.")
    
class Carnivore (Mammal): # Carnivore inherits from Mammal
  def __init__(self, name): # Carnivore's constructor
    Mammal.__init__(self, name, "meat") # Mammal's constructor 
    print ("I eat meat.")
lion = Carnivore("lion") # lion is an instance of Carnivore

However, if we move the print method in a separate method, the subclass can not only access the method of its parent class—but also override it if needed. This behavior is shown in the highlighted lines of the following code:

Python 3.10.4
class Animal ():
  def __init__(self, name, food, characteristic):
    self.name = name
    self.characteristic = characteristic
    self.food = food
  def printer(self):
    print ("I am a " + str(self.name) + ".")
    
class Mammal (Animal):
  def __init__(self, name, food):
    Animal.__init__(self, name, food, "warm blooded")
  def printer(self):
    print ("I am warm blooded.")
    
class Carnivore (Mammal):
  def __init__(self, name):
    Mammal.__init__(self, name, "meat")
  def printer(self):
    print ("I eat meat.")
lion = Carnivore("lion")
lion.printer()

Now if you remove the printer() method of the Carnivore class in lines 18, 19, the lion object will be able to access the printer() method of its super/parent class Mammal. The output will then become:

I am warm blooded.

If you also remove the printer() method in 12, 13 of the Mammal class, the lion object will access the printer() method of its superclass Animal. It will then print:

I am a lion.

In the next lesson, we will discuss multiple inheritance; it’s slightly different from multi-level inheritance.