Borrowing System

Part of the Object Oriented Programming section of Coddy's Python journey — lesson 57 of 64.

Challenge

Medium

In this challenge, you'll implement a library management system with borrowing functionality.

Implement the required functionality in the following files:

book.py - Contains Book class definition
user.py - Contains User class definition
library.py - Contains Library class where you'll implement the borrow_book method

Follow the TODO comments in each file for step-by-step implementation guidance. The borrow_book method should handle various scenarios including book/user not found and availability checks.

Cheat sheet

This challenge focuses on implementing a library management system using object-oriented programming principles. The system involves three main classes:

Book class - Represents individual books in the library
User class - Represents library users who can borrow books
Library class - Manages the collection of books and handles borrowing operations

The key functionality involves implementing a borrow_book method that handles:

Checking if books and users exist in the system
Verifying book availability before lending
Managing the borrowing process between users and books

Try it yourself

from book import Book
from user import User
from library import Library
import random

# Comprehensive test case handler
test_case = input()

# Basic functionality tests
if test_case == "borrow_success":
    library = Library("Community Library")
    
    # Add books and users
    book = Book("The Great Gatsby", "F. Scott Fitzgerald", "123456")
    library.add_book(book)
    
    user = User("U001", "Alice")
    library.add_user(user)
    
    # Borrow book
    result = library.borrow_book("123456", "U001")
    print(result)
    print(f"Book available: {book.available}")
    print(f"Books borrowed by user: {len(user.books_borrowed)}")

elif test_case == "book_not_found":
    library = Library("Community Library")
    user = User("U001", "Alice")
    library.add_user(user)
    
    result = library.borrow_book("nonexistent", "U001")
    print(result)

elif test_case == "user_not_found":
    library = Library("Community Library")
    book = Book("The Great Gatsby", "F. Scott Fitzgerald", "123456")
    library.add_book(book)
    
    result = library.borrow_book("123456", "nonexistent")
    print(result)
    
elif test_case == "book_not_available":
    library = Library("Community Library")
    
    # Add books and users
    book = Book("The Great Gatsby", "F. Scott Fitzgerald", "123456")
    book.available = False  # Book is already borrowed
    library.add_book(book)
    
    user = User("U001", "Alice")
    library.add_user(user)
    
    # Try to borrow unavailable book
    result = library.borrow_book("123456", "U001")
    print(result)

# Edge cases and additional tests
elif test_case == "multiple_books":
    library = Library("Community Library")
    user = User("U001", "Alice")
    library.add_user(user)
    
    # Create multiple books
    books = [
        Book("Book 1", "Author 1", "111"),
        Book("Book 2", "Author 2", "222"),
        Book("Book 3", "Author 3", "333")
    ]
    
    for book in books:
        library.add_book(book)
    
    # Borrow multiple books
    results = []
    for book in books:
        results.append(library.borrow_book(book.isbn, "U001"))
    
    for result in results:
        print(result)
    
    print(f"Total books borrowed: {len(user.books_borrowed)}")

elif test_case == "multiple_users":
    library = Library("Community Library")
    book = Book("Popular Book", "Famous Author", "999")
    library.add_book(book)
    
    # Create multiple users
    users = [
        User("U001", "Alice"),
        User("U002", "Bob"),
        User("U003", "Charlie")
    ]
    
    for user in users:
        library.add_user(user)
    
    # Try to borrow the same book with different users
    result1 = library.borrow_book("999", "U001")
    result2 = library.borrow_book("999", "U002")  # Should fail
    
    print(result1)
    print(result2)
    print(f"Book's borrower: {book.borrower.name}")

elif test_case == "return_book":
    library = Library("Community Library")
    book = Book("The Great Gatsby", "F. Scott Fitzgerald", "123456")
    library.add_book(book)
    
    user = User("U001", "Alice")
    library.add_user(user)
    
    # Borrow the book
    borrow_result = library.borrow_book("123456", "U001")
    print(borrow_result)
    
    # Verify book status
    print(f"Book available: {book.available}")
    print(f"Book borrower: {book.borrower.name}")
    print(f"User's borrowed books: {len(user.books_borrowed)}")
    print(f"First borrowed book title: {user.books_borrowed[0].title}")

elif test_case == "empty_library":
    library = Library("Empty Library")
    result = library.borrow_book("any_isbn", "any_user_id")
    print(result)

elif test_case == "stress_test":
    library = Library("Large Library")
    
    # Create and add 100 books
    for i in range(1, 101):
        book = Book(f"Book {i}", f"Author {i}", f"ISBN-{i}")
        library.add_book(book)
    
    # Create and add 50 users
    for i in range(1, 51):
        user = User(f"U{i:03d}", f"User {i}")
        library.add_user(user)
    
    # Perform 200 borrow operations
    successful = 0
    book_not_found = 0
    user_not_found = 0
    not_available = 0
    
    for _ in range(200):
        # Generate random ISBNs and user IDs (some valid, some invalid)
        isbn = f"ISBN-{random.randint(1, 120)}"  # Some will be invalid
        user_id = f"U{random.randint(1, 60):03d}"  # Some will be invalid
        
        result = library.borrow_book(isbn, user_id)
        
        if result == "Book borrowed successfully":
            successful += 1
        elif result == "Book not found":
            book_not_found += 1
        elif result == "User not found":
            user_not_found += 1
        elif result == "Book is not available":
            not_available += 1
    
    print(f"Successful borrows: {successful}")
    print(f"Book not found: {book_not_found}")
    print(f"User not found: {user_not_found}")
    print(f"Book not available: {not_available}")

elif test_case == "borrower_reference":
    library = Library("Community Library")
    book = Book("The Great Gatsby", "F. Scott Fitzgerald", "123456")
    library.add_book(book)
    
    user = User("U001", "Alice")
    library.add_user(user)
    
    # Borrow the book
    library.borrow_book("123456", "U001")
    
    # Verify references
    print(f"Book's borrower name: {book.borrower.name}")
    print(f"First book in user's borrowed list: {user.books_borrowed[0].title}")