Section 4: Object-Oriented Programming (OOP)

Lesson 1: Introduction to OOP in Python

1.1 Classes and Objects

Object-Oriented Programming (OOP) is a paradigm that revolves around the concept of classes and objects. A class is a blueprint for creating objects, and objects are instances of classes.

Example: 

# Class definition

class Dog:

    def __init__(self, name, age):

        self.name = name

        self.age = age

    def bark(self):

        print("Woof!")

# Creating objects

dog1 = Dog("Buddy", 3)

dog2 = Dog("Max", 5)

# Accessing object attributes and methods

print(dog1.name)  # Output: Buddy

dog2.bark()       # Output: Woof!

1.2 Inheritance, Encapsulation, and Polymorphism

Inheritance: Allows a class (subclass) to inherit properties and methods from another class (superclass).

Example:

# Inheritance

class Student:

    def __init__(self, name, age):

        self.name = name

        self.age = age

class GraduateStudent(Student):

    def __init__(self, name, age, program):

        super().__init__(name, age)

        self.program = program

grad_student = GraduateStudent("Alice", 25, "Computer Science")

print(grad_student.name)     # Output: Alice

Encapsulation: Restricts access to certain components of a class and prevents the accidental modification of data.

Example: 

# Encapsulation

class BankAccount:

    def __init__(self, balance):

        self.__balance = balance

    def get_balance(self):

        return self.__balance

account = BankAccount(1000)

print(account.get_balance())  # Output: 1000

Polymorphism: Enables a single interface to represent different types. In Python, it often involves method overloading or overriding.

Example:

# Polymorphism

class Shape:

    def area(self):

        pass

class Circle(Shape):

    def __init__(self, radius):

        self.radius = radius

    def area(self):

        return 3.14 * self.radius ** 2

class Square(Shape):

    def __init__(self, side):

        self.side = side

    def area(self):

        return self.side ** 2

circle = Circle(5)

square = Square(4)

print(circle.area())  # Output: 78.5

print(square.area())  # Output: 16

Lesson 2: File Handling

2.1 Reading and Writing to Files

File handling is essential for reading from and writing to files. Python provides built-in functions for these operations.

Example: 

# Reading and writing to files

with open("example.txt", "w") as file:

    file.write("Hello, Python!")

with open("example.txt", "r") as file:

    content = file.read()

    print(content)  # Output: Hello, Python!

2.2 Working with Different File Formats (txt, csv)

Python supports various file formats. Working with CSV files, for instance, involves using the csv module.

Example: 

# Working with CSV files

import csv

data = [

    ["Name", "Age", "City"],

    ["Alice", 25, "New York"],

    ["Bob", 30, "San Francisco"]

]

with open("data.csv", "w", newline="") as csvfile:

    csv_writer = csv.writer(csvfile)

    csv_writer.writerows(data)

with open("data.csv", "r") as csvfile:

    csv_reader = csv.reader(csvfile)

    for row in csv_reader:

        print(row)

        # Output:

        # ['Name', 'Age', 'City']

        # ['Alice', '25', 'New York']

        # ['Bob', '30', 'San Francisco']

In Section 4, we delved into Object-Oriented Programming (OOP) in Python, introducing the concepts of classes, objects, inheritance, encapsulation, and polymorphism. OOP provides a powerful paradigm for structuring code and creating reusable, maintainable software.

Additionally, we explored file handling in Python, covering the basics of reading from and writing to files. Working with different file formats, such as text (txt) and comma-separated values (csv), allows for efficient data storage and retrieval.

As you incorporate OOP principles and file handling into your Python projects, you'll gain the ability to design more modular, scalable, and organized code. These concepts form a solid foundation for building complex and robust applications in Python.