What is Inheritance in OOP in Python? What are the Different Types of Inheritance
Published: 2024-01-11 17:21:11

We all have ever encountered the term **OOP**s (Object-Oriented Programming) in programming. OOP is an integral part of any programming language that helps carry out complex concepts. It provides a way to structure and organize the code in such a manner that makes it easier to maintain and scale the code.

Classes are an essential concept in OOP or we can say that classes are the building blocks of Object-Oriented Programming which is a programming model based on objects and classes.

Object-Oriented Programming has four important concepts and one of them is **inheritance**.

## What is Inheritance?

**Inheritance** can be defined as the mechanism that permits the newly created classes to inherit the methods and attributes of the existing class or parent class. The classes that inherit the methods and attributes from the parent class are called **subclass** and the existing class is called a **superclass**.

As soon as a subclass inherits the superclass, it gains all of the methods and attributes of the superclass. This allows us to reuse the code as well as we can extend or modify the behaviour of the superclass.

For example-

```python
class Hero:
    def power(self):
        print("Rich")

class Ironman(Hero):
    def speciality(self):
        print("Genius", "Millionaire", "Playboy", "Philanthropist")

obj = Ironman()
obj.power()
obj.speciality()
```

The class `Hero` has a method `power` that returns a specific power a hero has. Then we created a subclass `Ironman` that inherits the superclass `Hero` and the subclass `Ironman` has its own method `speciality` that specifies the specialities of Ironman.

The subclass `Ironman` now has access to all the attributes and methods of the superclass `Hero` as well.

We accessed the method `power` using the class `Ironman` which inherited the method `power` from the class `Hero`.

```bash
Rich
Genius Millionaire Playboy Philanthropist
```

Inheritance helps us reduce the effort that we put into writing the same logic again and again and makes it easy to maintain and update the code.

Different types of inheritance:

* **Single Inheritance**
    
* **Multiple Inheritance**
    
* **Multilevel Inheritance**
    
* **Hierarchical Inheritance**
    
* **Hybrid Inheritance**
    

## Single Inheritance


![Single Inheritance](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/uaqudwaxcsjqwholgbtd.png)

**Single inheritance** can be defined as an inheritance where a **subclass** or **derived class** inherits from a single **superclass** or **parent class**.

In simple words, the **derived class or subclass has only one direct parent class**. Here is an example of single inheritance.

```python
# Parent or Base Class
class Calculate:
    def sum(self, a, b):
        print(a + b)

# Subclass or Derived Class
class Number(Calculate):
    pass

obj = Number()
obj.sum(8, 90)

----------
98
```

The above code is no different from the code that we discussed earlier where we saw the first glimpse of class inheritance in Python.

The subclass `Number` inherited the superclass `Calculate` and now the methods inside it can now be accessed by the subclass `Number`. We created the instance for the subclass `Number` and then accessed the `sum` function from the superclass or parent class `Calculate`.

## Using constructor

Until now, we saw a simple demonstration of the class inheritance in which a subclass gains the methods and attributes of the superclass by just passing it as an argument.

Now we'll see how to perform inheritance when a class has a constructor function.

```python
# Base class
class Hero:
    # Constructor function
    def __init__(self, reel_name, hero_name):
        self.reel_name = reel_name
        self.hero_name = hero_name

    def show(self):
        print(self.reel_name)
        print(self.hero_name)

# Derived class
class Name(Hero):
    def __init__(self, real_name, reel_name, hero_name):
        self.real_name = real_name
        # Calling the __init__ of the parent class
        Hero.__init__(self, reel_name, hero_name)

    def display(self):
        print(self.real_name)
        Hero.show(self)

obj = Name("RDJ", "Tony Stark", "IronMan")
obj.display()
print("-"*20)
obj.show()
```

In the above code, we created the base class `Hero` and inside it, we defined the constructor function that takes two arguments `reel_name` and `hero_name` and then we defined the function `show` that prints the `reel_name` and `hero_name`.

Then we created a subclass `Name` that inherits the superclass `Hero` and then we created a constructor function that takes three arguments `real_name`, `reel_name`, and `hero_name`.

In order to access the objects of the parent class `Hero`, we invoked `__init__` of the parent class `Hero` and passed the required arguments.

Next, we created a function `display` that prints the `real_name` and calls the function `show` from the class `Hero`.

Then we created `obj` an instance of the class `Name` and called the function `display` and `show`.

```bash
RDJ
Tony Stark
IronMan
--------------------
Tony Stark
IronMan
```

**What if we didn't call the** `__init__` **of the parent class?**

```python
class Cal:
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def sq(self):
        print(self.a ** self.b)

class X(Cal):
    def __init__(self, c):
        self.c = c

obj = X("Hello")
obj.sq()
```

We have done everything similar to what we did earlier but this time we didn't call the `__init__` of the parent class `Cal` and tried to call the function `sq` from it.

```bash
Traceback (most recent call last):
  ...
    print(self.a ** self.b)
AttributeError: 'X' object has no attribute 'a'
```

We encountered an error and this happened because the objects of the parent class `Cal` were not available for the subclass or child class `X`.

## Multiple Inheritance


![Multiple Inheritance](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/lv7gxa8vkx9nkbtacy6b.png)

Python supports **multiple-class inheritance** and can be defined as an inheritance where a subclass or child class inherits from more than one superclass.

In short, **a subclass has more than one direct parent class or superclass**. Let's understand the concept of multiple-class inheritance with an example.

```python
# First Parent Class
class First:
    def __init__(self):
        self.greet = "Hello"

# Second Parent Class
class Second:
    def __init__(self):
        self.name = "Geeks"

# Child or Derived Class
class Child(First, Second):
    def __init__(self):
        First.__init__(self)
        Second.__init__(self)

    def combine(self):
        print(self.greet, self.name)
        print("Welcome to GeekPython.")

obj = Child()
obj.combine()
```

In the above code, subclass `Child` inherited two superclasses named `First` and `Second` that will help gain the attributes of both superclasses inside the subclass `Child`.

We then created a function `combine` that prints the values of `self.greet` and `self.name` and a string. We created `obj` which is an instance of the class and then called the `combine` function.

```bash
Hello Geeks
Welcome to GeekPython.
```

Note: There is a risk of using multiple inheritances because it can lead to uncertainty in the code and also cause a "**Diamond Problem**" where a subclass inherits certain conflicting methods from multiple parent classes.

## Diamond Problem

The "**Diamond Problem**" often occurs primarily in the case of multiple inheritance where a subclass inherits the conflicting methods from the multiple superclasses that eventually create ambiguity in the code.

```python
# Base Class
class Hello:
    def func(self):
        print("Hello")

# Derived Class
class Geek(Hello):
    def func(self):
        print("Geeks")

# Derived Class
class Python(Hello):
    def func(self):
        print("GeekPython")

# Derived Class
class GeekPython(Geek, Python):
    pass

obj = GeekPython()
obj.func()
```

In the above code, subclasses `Geek` and `Python` inherit from the superclass `Hero` and then another subclass `GeekPython` inherits from the subclasses `Geek` and `Python`. They all have a function with the same name `func`.

Now when we call the `func`, the order of the parent class decides from which class `GeekPython` inherits from. So, in this case, the function `func` inside the class `Geek` will get executed.

```bash
Geeks
```

**If we change the order of the class, then we'll get the following output**.

```python
# Derived Class
class GeekPython(Python, Geek):
    pass

----------
GeekPython
```

## Multi-level Inheritance


![Multi-level Inheritance](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/k4xo2p76yyh4bzqn7rcf.png)

**Multi-level inheritance** can be defined as where a **subclass** inherits from the **single subclass** and then **another subclass** inherits from the **first subclass**. By this, the second subclass can access all the attributes and methods from both the first subclass and the superclass.

Let's understand with an example showing multi-level inheritance.

```python
# Base Class
class GrandPa:
    def __init__(self):
        self.age = 100

# Derived CLass
class Parent(GrandPa):
    def __init__(self):
        self.name = "Geek"
        GrandPa.__init__(self)

# Derived Class
class GrandChild(Parent):
    def __init__(self):
        self.hobby = "Gaming"
        Parent.__init__(self)

    def display(self):
        print("Grandpa:", self.age)
        print("Parent:", self.name)
        print("Grandchild:", self.hobby)

obj = GrandChild()
obj.display()
```

In the above code, the subclass `Parent` inherits from the superclass `GrandPa` and now the first subclass `Parent` has access to the methods of the superclass `GrandPa`.

Then another subclass `GrandChild` inherited from the first subclass `Parent` and it has access to the methods that both the first subclass and superclass have.

```bash
Grandpa: 100
Parent: Geek
Grandchild: Gaming
```

## Hierarchical Inheritance


![Hierarchical Inheritance](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/dhlp1syjzg3q4dtz3h4c.png)

**Hierarchical inheritance** can be defined as when **more than one derived class inherits from a single base class**. Let's understand with an example.

```python
# Base Class
class Calculate:
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def division(self):
        print(self.a / self.b)

# Derived Class
class Add(Calculate):
    def __init__(self, a, b):
        Calculate.__init__(self, a, b)

    def add(self):
        print("Addition:", self.a + self.b)
        Add.division(self)

# Derived Class
class Subtract(Calculate):
    def __init__(self, a, b):
        Calculate.__init__(self, a, b)

    def subtract(self):
        print("Subtraction:", self.a - self.b)
        Subtract.division(self)

obj1 = Add(34, 98)
obj2 = Subtract(45, 67)
obj1.add()
obj2.subtract()
```

In the above code, both derived class `Add` and `Subtract` inherited from the superclass or base class `Calculate`.

```bash
Addition: 132
0.3469387755102041
Subtraction: -22
0.6716417910447762
```

## Hybrid Inheritance


![Hybrid Inheritance](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/j5vcy10vugpic4ie792c.png)

This type of inheritance is a blend of different inheritance which means it has a combination of two different types of inheritance like multiple or multi-level inheritances or multiple or single inheritances.

Here is an example showing the demonstration of **hybrid inheritance**.

```python
# Base Class
class Role:
    def role(self):
        print("Protagonist")

# Derived Class
class Luffy(Role):
    def power(self):
        print("Gum-Gum devil fruit")

# Derived Class
class Naruto(Role):
    def power1(self):
        print("Nine-tail fox")

# Derived Class
class Anime(Luffy, Naruto):
    def anime(self):
        print("They are anime characters.")

obj = Anime()
obj.role()
obj.power()
print("-"*20)
obj.role()
obj.power1()
print("-"*20)
obj.anime()
```

In the above code, the subclasses `Luffy` and `Naruto` inherit from the superclass `Role` and then the subclass Anime inherits from the subclasses `Luffy` and `Naruto`.

The first scenario where `Luffy` and `Naruto` inherit from the superclass `Role` shows the **single inheritance** and the second scenario where `Anime` inherits from the subclasses `Luffy` and `Naruto` shows the multiple inheritances.

```bash
Protagonist
Gum-Gum devil fruit
--------------------
Protagonist
Nine-tail fox
--------------------
They are anime characters.
```

## Conclusion

**Inheritance** is one of the pillars of **Object-Oriented Programming** (OOP) that allows a new class to inherit the methods and attributes of an existing class or parent class.

Python is one of the programming languages that support multiple inheritance of the class but it could lead to uncertainty in the code.

Let's review what we've learned:

We saw the concepts of different types of inheritance in Python:

* **Single Inheritance**
    
* **Multiple Inheritance**
    
* **Multi-level Inheritance**
    
* **Hierarchical Inheritance**
    
* **Hybrid Inheritance**
    

---

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---

**That's all for now**

**Keep Coding✌✌**