Module 050: Milestone Project — Library/Inventory Management System

Phase: 5. OOP | Estimated time: 3 hours | Milestone Project: Yes

Prerequisites

All modules 041-049 (Phase 5: OOP)

Learning Objectives

By the end of this module, you will be able to:

Design and implement a multi-class OOP system
Use inheritance to model specialized behavior
Demonstrate encapsulation with private/protected attributes
Use dunder methods (__str__, __repr__, __len__) for integration
Apply polymorphism and duck typing
Optionally use ABCs for interface contracts

Why This Matters

This milestone project ties together everything from Phase 5: classes, attributes, methods, constructors, class/instance variables, encapsulation, inheritance, polymorphism, dunder methods, and abstract base classes. You'll build a complete library management system demonstrating professional OOP design.

Project Overview

Build a Library Management System with three core classes: Book, Member, and Library. The system should handle adding/borrowing/returning books, tracking members, and enforcing borrowing limits.

Core Classes

class Book:
    """Represents a book in the library."""

    def __init__(self, title, author, isbn, copies=1):
        self.title = title
        self.author = author
        self.isbn = isbn
        self._copies = copies
        self._available = copies

    # Properties, dunder methods, and methods

class Member:
    """Represents a library member."""

    def __init__(self, name, member_id):
        self.name = name
        self.member_id = member_id
        self.borrowed_books = []

    def borrow_book(self, book):
        """Borrow a book from the library."""

    def return_book(self, book):
        """Return a borrowed book."""

class Library:
    """Manages the collection of books and members."""

    def __init__(self, name):
        self.name = name
        self.books = {}
        self.members = {}

    def add_book(self, book):
        """Add a book to the library."""

    def add_member(self, member):
        """Register a member."""

    def borrow_book(self, member_id, isbn):
        """Allow a member to borrow a book."""

    def return_book(self, member_id, isbn):
        """Process a book return."""

    def list_books(self):
        """List all books in the library."""

    def list_members(self):
        """List all registered members."""

Inheritance: Member Types

StudentMember: Can borrow up to 3 books, 14-day loan period
TeacherMember: Can borrow up to 10 books, 30-day loan period

Required Features

Add books with title, author, ISBN, and copy count
Register members (Student or Teacher)
Borrow a book (decrease available copies, add to member's list)
Return a book (increase available copies, remove from member's list)
List all books with availability
List all members with their borrowed books
Enforce borrowing limits per member type
Prevent borrowing unavailable books
Use @property for controlled attribute access
Implement __str__ and __repr__ on all classes

Extension Ideas

Add a search_books(title) or search_by_author(author) method
Add a get_borrowing_history(member_id) method
Add overdue tracking with fines
Add a @dataclass version of Book
Add Reservable mixin for reserving books

Key Takeaways

OOP organizes complex systems into interacting classes.
Inheritance models specialized behavior (Student vs Teacher members).
Encapsulation protects internal state (available copies, borrowed lists).
Dunder methods make objects work with Python built-ins.
A well-designed class hierarchy is reusable and extensible.

Next Module

Continue to Module 051 (Phase 6: Advanced OOP).

Project Instructions

See project/README.md for detailed instructions. The project/starter_code.py file contains a skeleton to complete. A full solution is in project/solution/library_system.py.

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