OOP Concepts

OOP Concepts

This page is a reference for the Object-Oriented Programming concepts I'm learning and practicing in Python.

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Classes

A class is a blueprint for creating objects.

Classes can contain attributes and methods that describe what an object has and what it can do.

Example projects where I use classes:

• Pet Simulator
• Employee Payroll System
• Student Grade System
• Recipe Book
• Library System

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Objects

An object is an instance of a class.

For example, if Pet is a class, an individual pet created from that class is an object.

Objects can have their own data while using the same structure from the class.

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__init__()

The __init__() method runs when a new object is created.

It is commonly used to give an object its starting attributes.

Example:

class Pet:
    def __init__(self):
        self.hunger = 50
        self.happiness = 50

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self

self refers to the current object.

It allows each object to access and change its own attributes and methods.

For example:

self.hunger
self.happiness
self.name

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Attributes

Attributes store information about an object.

For example, a Pet object might have:

name
hunger
happiness
energy

Different objects can have different values for the same attributes.

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Methods

Methods are functions that belong to a class.

They can be used to make an object perform an action or change its data.

For example, a pet could have methods such as:

feed()
play()
sleep()
update_state()

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Encapsulation

Encapsulation is the idea of keeping data and the methods that work with that data together inside a class.

It can also be used to control how certain data is accessed or changed.

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Inheritance

Inheritance allows one class to use attributes and methods from another class.

For example:

Animal
  ↓
Pet
  ↓
Dog

A Dog class could inherit common features from Pet instead of having to recreate everything.

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Polymorphism

Polymorphism allows different classes to use the same method name while behaving differently.

For example, different types of pets could all have a:

make_sound()

method, but each type of pet could produce a different result.

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Composition

Composition is when one class contains or uses objects from another class.

For example, a Library could contain multiple Book objects.

Library
├── Book
├── Book
└── Book

This is useful for building larger programs out of smaller classes.

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Lists of Objects

Python lists can store multiple objects from a class.

For example, a library could have:

books = [book1, book2, book3]

This is useful when building systems with multiple students, employees, books, pets, or other objects.

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OOP Concepts I Want to Practice

• Classes
• Objects
• __init__()
• self
• Attributes
• Methods
• Encapsulation
• Inheritance
• Polymorphism
• Composition
• Lists of objects
• Multiple classes working together
• Larger OOP projects