Python Inner Classes

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Python Inner Classes

An inner class is a class defined inside another class.

It is mainly used when a class is closely related to another class and is not useful on its own.

Inner classes help:

• Organize related code
• Improve readability
• Limit the scope of helper classes

Defining an Inner Class

A class can be declared inside another class just like a method.

Example: Creating a basic inner class

class Container: def __init__(self): self.title = "Main Container" class Item: def show(self): print("This is an item inside the container") box = Container() print(box.title)

Main Container

Accessing an Inner Class from Outside

To use an inner class, you must first create an object of the outer class, then create an object of the inner class using that instance.

Example: Accessing and using an inner class

class Library: def __init__(self): self.name = "City Library" class Book: def info(self): print("Book belongs to the library") library = Library() book = library.Book() book.info()

Book belongs to the library

Accessing Outer Class Data from an Inner Class

By default, an inner class does not automatically know about the outer class instance.

To access outer class data, pass the outer object explicitly.

Example: Passing the outer class instance

class Profile: def __init__(self): self.username = "guest_user" class Settings: def __init__(self, profile): self.profile = profile def display(self): print("Profile username:", self.profile.username) profile = Profile() settings = profile.Settings(profile) settings.display()

Profile username: guest_user

Practical Use Case of Inner Classes

Inner classes are useful for modeling components that belong to a larger object.

Example: Using an inner class to represent a laptop’s battery

class Laptop: def __init__(self, brand): self.brand = brand self.battery = self.Battery() class Battery: def __init__(self): self.level = 0 def charge(self): self.level = 100 print("Battery fully charged") def drain(self): self.level = 10 print("Battery low") def use(self): if self.battery.level > 20: print(f"Using the {self.brand} laptop") else: print("Please charge the battery first") lap = Laptop("Dell") lap.use() lap.battery.charge() lap.use()

Please charge the battery first Battery fully charged Using the Dell laptop

Using Multiple Inner Classes

An outer class can contain more than one inner class to represent different components.

Example: Multiple inner classes inside one class

class Smartphone: def __init__(self): self.camera = self.Camera() self.speaker = self.Speaker() class Camera: def capture(self): print("Photo captured") class Speaker: def play_sound(self): print("Playing sound") phone = Smartphone() phone.camera.capture() phone.speaker.play_sound()

Photo captured Playing sound

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