Python Tutorials · Python Classes

Python Inner Classes

Learn all about Python Inner Classes in this comprehensive tutorial.

5 min read beginner

•An inner class is a class defined inside another class.
•To access the inner class, create an object of the outer class, and then create an object of the inner class:
•Inner classes in Python do not automatically have access to the outer class instance.
•Inner classes are useful for creating helper classes that are only used within the context of the outer class:
•A class can have multiple inner classes:

Python Inner Classes

An inner class is a class defined inside another class. The inner class can access the properties and methods of the outer class.

Inner classes are useful for grouping classes that are only used in one place, making your code more organized.

python

class Outer:  def __init__(self):    self.name = "Outer Class"  class Inner:    def __init__(self):      self.name = "Inner Class"    def display(self):      print("This is the inner class")outer = Outer()print(outer.name)

Accessing Inner Class from the Outside

To access the inner class, create an object of the outer class, and then create an object of the inner class:

python

class Outer:  def __init__(self):    self.name = "Outer"  class Inner:    def __init__(self):      self.name = "Inner"    def display(self):      print("Hello from inner class")outer = Outer()inner = outer.Inner()inner.display()

Accessing Outer Class from Inner Class

Inner classes in Python do not automatically have access to the outer class instance.

If you want the inner class to access the outer class, you need to pass the outer class instance as a parameter:

python

class Outer:  def __init__(self):    self.name = "Emil"  class Inner:    def __init__(self, outer):      self.outer = outer    def display(self):      print(f"Outer class name: {self.outer.name}")outer = Outer()inner = outer.Inner(outer)inner.display()

Practical Example

Inner classes are useful for creating helper classes that are only used within the context of the outer class:

python

class Car:  def __init__(self, brand, model):    self.brand = brand    self.model = model    self.engine = self.Engine()  class Engine:    def __init__(self):      self.status = "Off"    def start(self):      self.status = "Running"      print("Engine started")    def stop(self):      self.status = "Off"      print("Engine stopped")  def drive(self):    if self.engine.status == "Running":      print(f"Driving the {self.brand} {self.model}")    else:      print("Start the engine first!")car = Car("Toyota", "Corolla")car.drive()car.engine.start()car.drive()

Multiple Inner Classes

A class can have multiple inner classes:

python

class Computer:  def __init__(self):    self.cpu = self.CPU()    self.ram = self.RAM()  class CPU:    def process(self):      print("Processing data...")  class RAM:    def store(self):      print("Storing data...")computer = Computer()computer.cpu.process()computer.ram.store()

Module quiz

2 questions

Which of the following is true about Python Inner Classes?

It is strictly typedIt is evaluated at runtimeIt requires explicit memory managementIt is deprecated

What is the most common pitfall when working with Python Inner Classes?

SyntaxErrorIndentationErrorNameErrorTypeError

Answer all questions to submit.

Python Encapsulation

Python File Handling

Python Inner Classes

AI Summary

Python Inner Classes

Accessing Inner Class from the Outside

Accessing Outer Class from Inner Class

Practical Example

Multiple Inner Classes

Module quiz