Comparison magic methods in Python - Mini Project: Build & Apply

Comparison Magic Methods

📖 Scenario: Imagine you are creating a simple program to compare books by their number of pages. You want to be able to say if one book is shorter, longer, or the same length as another book.

🎯 Goal: You will build a Book class that can compare two books using comparison operators like <, >, and ==. This will help you easily check which book is longer or if they have the same length.

📋 What You'll Learn

Create a Book class with a title and pages attributes

Add a variable called book1 with title 'Python Basics' and 150 pages

Add a variable called book2 with title 'Advanced Python' and 200 pages

Add a variable called book3 with title 'Python Basics' and 150 pages

Implement the __lt__ method to compare books by pages

Implement the __eq__ method to check if two books have the same pages

Print the results of book1 < book2 and book1 == book3

💡 Why This Matters

🌍 Real World

Comparison magic methods let you compare custom objects easily, like sorting products by price or comparing students by grades.

💼 Career

Understanding these methods is useful for software development jobs where you create classes that need to be compared or sorted, such as in data processing or game development.

1

Create the Book class and book variables

Create a class called Book with an __init__ method that takes title and pages as parameters and stores them as attributes. Then create three variables: book1 with title 'Python Basics' and 150 pages, book2 with title 'Advanced Python' and 200 pages, and book3 with title 'Python Basics' and 150 pages.

Python

# Your code here

Need a hint?

Remember to define the __init__ method inside the Book class and assign the parameters to self.title and self.pages. Then create the three book variables exactly as described.

2

Add the __lt__ method to compare books by pages

Inside the Book class, add a method called __lt__ that takes self and other as parameters. It should return True if self.pages is less than other.pages, otherwise False.

Python

class Book:
    def __init__(self, title, pages):
        self.title = title
        self.pages = pages

    # Add __lt__ method here

book1 = Book('Python Basics', 150)
book2 = Book('Advanced Python', 200)
book3 = Book('Python Basics', 150)

Need a hint?

The __lt__ method is called when you use the < operator. It should compare the pages attribute of self and other.

3

Add the __eq__ method to check if books have the same pages

Inside the Book class, add a method called __eq__ that takes self and other as parameters. It should return True if self.pages is equal to other.pages, otherwise False.

Python

class Book:
    def __init__(self, title, pages):
        self.title = title
        self.pages = pages

    def __lt__(self, other):
        return self.pages < other.pages

    # Add __eq__ method here

book1 = Book('Python Basics', 150)
book2 = Book('Advanced Python', 200)
book3 = Book('Python Basics', 150)

Need a hint?

The __eq__ method is called when you use the == operator. It should compare the pages attribute of self and other.

4

Print comparison results between book1 and book2

Write two print statements: one that prints the result of book1 < book2 and another that prints the result of book1 == book3.

Python

class Book:
    def __init__(self, title, pages):
        self.title = title
        self.pages = pages

    def __lt__(self, other):
        return self.pages < other.pages

    def __eq__(self, other):
        return self.pages == other.pages

book1 = Book('Python Basics', 150)
book2 = Book('Advanced Python', 200)
book3 = Book('Python Basics', 150)

# Print comparison results below
# Your code here

Need a hint?

Use print(book1 < book2) and print(book1 == book3) to show the comparison results.