Explain the Python Inner Classes

Question

Anubhav Kumar · Answer

In Python, an inner class (also called a 
nested class) is a class defined inside another class. Inner classes are often used when you want to logically group classes that are only used within the context of their enclosing class — similar to
namespacing or encapsulation.
Let’s break it down with examples and explanations:
1. Basic Syntax
class Outer:
    class Inner:
        def display(self):
            print("This is the Inner class")
    def show(self):
        print("This is the Outer class")
Usage:
obj_outer = Outer()
obj_outer.show()
# Access inner class through outer class
obj_inner = Outer.Inner()
obj_inner.display()
Output:
This is the Outer class
This is the Inner class
2. Why Use Inner Classes
Inner classes are used when:
You want to encapsulate helper classes that are not meant to be used outside the enclosing class.You want to group related functionality together.You want to improve code organization and readability.
3. Outer and Inner Relationship
Inner classes can access outer class members via an instance reference.
class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age
        self.address = self.Address("Pune", "Maharashtra")
    def show(self):
        print(f"Name: {self.name}, Age: {self.age}")
        self.address.display()
    class Address:
        def __init__(self, city, state):
            self.city = city
            self.state = state
        def display(self):
            print(f"City: {self.city}, State: {self.state}")
Usage:
p1 = Person("Anna", 25)
p1.show()
Output:
Name: Anna, Age: 25
City: Pune, State: Maharashtra
Here, Address is an inner class — it logically belongs only to 
Person.
4. Accessing Inner Class from Outside
You can create an instance of the inner class using the outer class name:
addr = Person.Address("Mumbai", "Maharashtra")
addr.display()
5. Real-World Example: Data Encapsulation
class Computer:
    def __init__(self):
        self.cpu = self.CPU()
        self.memory = self.Memory()
    def show_specs(self):
        print("Computer Specifications:")
        self.cpu.display()
        self.memory.display()
    class CPU:
        def display(self):
            print("Processor: Intel i7")
    class Memory:
        def display(self):
            print("RAM: 16GB")
Usage:
comp = Computer()
comp.show_specs()
Output:
Computer Specifications:
Processor: Intel i7
RAM: 16GB
6. Summary
Feature
Description
Definition
Class defined inside another class
Purpose
Encapsulation, grouping, logical structure
Access Syntax
Outer.Inner
Can Access Outer Members?
Only via outer instance if explicitly passed
Use Case
Helper classes used only by the outer class
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Explain the Python Inner Classes

Anubhav Kumar

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1 Answers

1. Basic Syntax

2. Why Use Inner Classes

3. Outer and Inner Relationship

4. Accessing Inner Class from Outside

5. Real-World Example: Data Encapsulation

6. Summary

Liked By

Feature	Description
Definition	Class defined inside another class
Purpose	Encapsulation, grouping, logical structure
Access Syntax	`Outer.Inner`
Can Access Outer Members?	Only via outer instance if explicitly passed
Use Case	Helper classes used only by the outer class