OOP Terminology in Python

Object-Oriented Programming (OOP) in Python uses specific terminology to describe its concepts. Understanding these terms is essential for working with classes, objects, and inheritance in Python.

Core OOP Terms

Class

A user-defined blueprint for creating objects that defines attributes and methods. Think of it as a template that describes what data and behaviors objects will have ?

class Car:
    wheels = 4  # Class variable
    
    def __init__(self, brand):
        self.brand = brand  # Instance variable
    
    def start_engine(self):  # Method
        return f"{self.brand} engine started"

# Creating an instance
my_car = Car("Toyota")
print(my_car.start_engine())

Toyota engine started

Object and Instance

An object is a unique instance of a class. Instantiation is the process of creating an object from a class ?

class Circle:
    def __init__(self, radius):
        self.radius = radius

# Instantiation - creating instances
circle1 = Circle(5)
circle2 = Circle(10)

print(f"Circle 1 radius: {circle1.radius}")
print(f"Circle 2 radius: {circle2.radius}")

Circle 1 radius: 5
Circle 2 radius: 10

Variables and Data Members

Class Variables vs Instance Variables

Class variables are shared by all instances, while instance variables belong to individual objects. Both are types of data members ?

class Student:
    school_name = "Python High"  # Class variable
    
    def __init__(self, name, grade):
        self.name = name      # Instance variable
        self.grade = grade    # Instance variable

student1 = Student("Alice", "A")
student2 = Student("Bob", "B")

print(f"School: {Student.school_name}")
print(f"Student 1: {student1.name}, Grade: {student1.grade}")
print(f"Student 2: {student2.name}, Grade: {student2.grade}")

School: Python High
Student 1: Alice, Grade: A
Student 2: Bob, Grade: B

Advanced OOP Concepts

Inheritance

The transfer of characteristics from a parent class to child classes, allowing code reuse and creating class hierarchies ?

class Animal:
    def __init__(self, name):
        self.name = name
    
    def speak(self):
        return f"{self.name} makes a sound"

class Dog(Animal):  # Dog inherits from Animal
    def speak(self):
        return f"{self.name} barks"

# Using inheritance
dog = Dog("Max")
print(dog.speak())

Max barks

Operator Overloading

Defining custom behavior for operators when used with objects of your class ?

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y
    
    def __add__(self, other):  # Operator overloading for +
        return Point(self.x + other.x, self.y + other.y)
    
    def __str__(self):
        return f"Point({self.x}, {self.y})"

p1 = Point(1, 2)
p2 = Point(3, 4)
p3 = p1 + p2  # Uses __add__ method

print(p3)

Point(4, 6)

Summary of OOP Terms

Conclusion

Understanding OOP terminology is crucial for Python programming. These concepts work together to create organized, reusable code through classes, objects, inheritance, and method definitions.