Python Inner Classes

🐍 Python Inner Classes — Complete Guide

In Python, a class defined inside another class is called an inner class (or nested class).
Inner classes are useful to group classes logically and hide implementation details.

1️⃣ Basic Syntax

2️⃣ Example: Using Inner Class to Organize Code

class University:
def __init__(self, name):
self.name = nameclass Department:
def __init__(self, dept_name):
self.dept_name = dept_namedef info(self):
print(f"Department: {self.dept_name}")

# Create objects
uni = University("ABC University")
dept = University.Department("Computer Science")

print(uni.name) # ABC University
dept.info() # Department: Computer Science

class University:

def __init__(self, name):

self.name = nameclass Department:

def __init__(self, dept_name):

self.dept_name = dept_namedef info(self):

print(f"Department: {self.dept_name}")

# Create objects

uni = University("ABC University")

dept = University.Department("Computer Science")

print(uni.name) # ABC University

dept.info() # Department: Computer Science

Inner class Department is logically part of University but independent.

3️⃣ Access Outer Class Attributes from Inner Class

Pass the outer class object to access its attributes inside inner class.

4️⃣ Inner Classes with Methods

5️⃣ Use Cases of Inner Classes

Logical grouping of classes
Encapsulation of helper classes
Avoid cluttering global namespace
Represent has-a relationships

Example: Car has-a Engine → Engine can be an inner class.

6️⃣ Access Outer Class Methods from Inner Class

7️⃣ Summary Table

Feature	Description
Inner Class	Class inside another class
Access Outer	Pass outer object to inner class
Use Case	Logical grouping, encapsulation
Instantiation	`Outer.Inner()`
Relationship	Often represents “has-a”

🔹 Example: Real-Life Inner Class

class Library:
def __init__(self, name):
self.name = nameclass Book:
def __init__(self, title, author):
self.title = title
self.author = authordef display(self):
print(f"{self.title} by {self.author}")

book1 = Library.Book("Python 101", "Vipul")
book1.display() # Python 101 by Vipul

class Library:

def __init__(self, name):

self.name = nameclass Book:

def __init__(self, title, author):

self.title = title

self.author = authordef display(self):

print(f"{self.title} by {self.author}")

book1 = Library.Book("Python 101", "Vipul")

book1.display() # Python 101 by Vipul

Inner class Book is part of Library logically, but you can instantiate it independently.

Python Inner Classes