Library-Management-System

Library Management System - Requirements Specification

Overview

Design and implement a Library Management System that demonstrates OOP principles, design patterns, and Python best practices. The system manages books, DVDs, members, and borrowing operations.

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Functional Requirements

FR1: Library Item Management

• FR1.1: Add library items (books and DVDs) with title, creator, and available copies (ID auto-generated)
• FR1.2: Remove library items from library
• FR1.3: Display all library items
• FR1.4: Search library items by title or creator

FR2: Book Management

• FR2.1: Add books with title, author, ISBN, and number of pages

FR3: DVD Management

• FR3.1: Add DVDs with title, director, duration, and genre

FR4: Member Management

• FR4.1: Add members with name and email (member_id auto-generated)
• FR4.2: Remove members from library
• FR4.3: Display all members
• FR4.4: Support different member types (Regular, Premium) with different borrow limits

FR5: Borrowing Operations

• FR5.1: Allow members to borrow library items (Regular: 3 items, Premium: 5 items)
• FR5.2: Allow members to return library items
• FR5.3: Show currently borrowed items by each member

FR6: Waiting List & Notification System

• FR6.1: Allow members to join waiting list for unavailable items
• FR6.2: Remove members from waiting list
• FR6.3: Notify all waiting members when an item becomes available
• FR6.4: Display waiting list for a specific item

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Class Design

1. LibraryItem (Abstract Base Class)

Attributes:

• id: int - Auto-generated ID (1, 2, 3, ...)
• title: str - Title of the item
• creator: str - Author for books, Director for DVDs
• total_copies: int - Total number of copies
• available_copies: int - Number of available copies
• _id_counter: int - Class variable for auto-increment

Methods:

• __init__(title, creator, copies) - Constructor
• is_available() -> bool - Check if item is available
• borrow() -> bool - Borrow the item
• return_item() -> bool - Return the item
• get_item_info() -> str - Abstract method to be overridden
• get_item_type() -> str - Abstract method to be overridden
• __str__() -> str - String representation
• __eq__(other) -> bool - Compare by ID

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2. Book (inherits LibraryItem)

Attributes:

• author: str - Author name (alias for creator)
• isbn: str - ISBN number
• num_pages: int - Number of pages

Methods:

• __init__(title, author, copies, isbn, num_pages) - Constructor
• get_item_type() -> str - Returns "Book"
• get_item_info() -> str - Override to include book details

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3. DVD (inherits LibraryItem)

Attributes:

• director: str - Director name (alias for creator)
• duration_minutes: int - Duration in minutes
• genre: str - Genre of the DVD

Methods:

• __init__(title, director, copies, duration_minutes, genre) - Constructor
• get_item_type() -> str - Returns "DVD"
• get_item_info() -> str - Override to include DVD details

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4. Member (Base Class - Observer)

Attributes:

• member_id: int - Auto-generated ID (1, 2, 3, ...)
• name: str - Member name
• email: str - Member email
• borrowed_items: List[int] - List of borrowed item IDs
• notifications: List[str] - List of notification messages
• MAX_BORROW_LIMIT: int - To be set by subclasses
• _id_counter: int - Class variable for auto-increment

Methods:

• __init__(name, email) - Constructor
• can_borrow() -> bool - Check if member can borrow more items
• borrow_item(item_id: int) -> bool - Borrow an item
• return_item(item_id: int) -> bool - Return an item
• get_borrowed_count() -> int - Get number of borrowed items
• get_max_borrow_limit() -> int - Abstract method to be overridden
• update(message: str) -> None - Observer method - receives notifications
• get_notifications() -> List[str] - Get all notifications
• clear_notifications() -> None - Clear all notifications
• __str__() -> str - String representation

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5. RegularMember (inherits Member)

Attributes:

• MAX_BORROW_LIMIT: int = 3 - Maximum 3 items

Methods:

• __init__(name, email) - Constructor
• get_max_borrow_limit() -> int - Returns 3

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6. PremiumMember (inherits Member)

Attributes:

• MAX_BORROW_LIMIT: int = 5 - Maximum 5 items
• membership_expiry: str - Optional expiry date

Methods:

• __init__(name, email, membership_expiry=None) - Constructor
• get_max_borrow_limit() -> int - Returns 5

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7. Library (Singleton + Subject/Observable)

Attributes:

• _instance: Library - Singleton instance
• items: Dict[int, LibraryItem] - item_id → LibraryItem mapping
• members: Dict[int, Member] - member_id → Member mapping
• waiting_list: Dict[int, List[Member]] - item_id → List of waiting Members

Methods:

• __new__(cls) -> Library - Singleton pattern implementation
• add_item(item: LibraryItem) -> bool - Add item to library
• remove_item(item_id: int) -> bool - Remove item from library
• add_member(member: Member) -> bool - Add member to library
• remove_member(member_id: int) -> bool - Remove member from library
• borrow_item(member_id: int, item_id: int) -> bool - Borrow an item
• return_item(member_id: int, item_id: int) -> bool - Return an item
• search_items(query: str) -> List[LibraryItem] - Search items by title or creator
• display_all_items() -> None - Display all items
• display_all_members() -> None - Display all members
• join_waiting_list(member_id: int, item_id: int) -> bool - Join waiting list
• leave_waiting_list(member_id: int, item_id: int) -> bool - Leave waiting list
• get_waiting_list(item_id: int) -> List[Member] - Get waiting list for an item
• notify_waiting_members(item_id: int) -> None - Notify all waiting members
• __len__() -> int - Returns total number of items

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OOP Concepts Demonstrated

Magic Methods

• __init__ - Constructor with auto-generated IDs
• __str__ - String representation
• __eq__ - Equality comparison
• __len__ - Return count
• __new__ - Singleton pattern

Four Pillars of OOP

1. Encapsulation - Private data with getter methods, class variables for ID counters
2. Abstraction - LibraryItem as abstract base class with abstract methods
3. Inheritance - LibraryItem → Book/DVD, Member → RegularMember/PremiumMember
4. Polymorphism - Method overriding (get_item_info, get_item_type, get_max_borrow_limit)

Design Patterns

• Singleton Pattern - Library class (only one instance exists)
• Observer Pattern - Members on waiting list get notified when item becomes available

SOLID Principles

• Single Responsibility - Each class has one clear purpose
• Open/Closed - Can extend with new item/member types without modifying existing code
• Liskov Substitution - Subclasses can replace base classes without breaking functionality

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Sample Usage

def main():
    print("=" * 70)
    print("LIBRARY MANAGEMENT SYSTEM - DEMO")
    print("=" * 70)
    
    # Create library (Singleton)
    library = Library()
    
    # Add books and DVDs
    book1 = Book("Python Crash Course", "Eric Matthes", 2, "978-1593279288", 544)
    book2 = Book("Clean Code", "Robert Martin", 2, "978-0132350884", 464)
    dvd1 = DVD("The Matrix", "Wachowski Brothers", 2, 136, "Sci-Fi")
    dvd2 = DVD("Inception", "Christopher Nolan", 1, 148, "Thriller")
    
    library.add_item(book1)
    library.add_item(book2)
    library.add_item(dvd1)
    library.add_item(dvd2)
    
    print(f"\n--- Added Items ---")
    print(f"Book: {book1} (ID: {book1.id})")
    print(f"DVD: {dvd1} (ID: {dvd1.id})")
    print(f"Total items: {len(library)}")
    
    # Demonstrate Polymorphism - get_item_info()
    print(f"\n--- Polymorphism Demo: get_item_info() ---")
    print(book1.get_item_info())
    print(f"\n{dvd1.get_item_info()}")
    
    # Add members
    alice = RegularMember("Alice", "alice@email.com")
    bob = PremiumMember("Bob", "bob@email.com")
    charlie = RegularMember("Charlie", "charlie@email.com")
    
    library.add_member(alice)
    library.add_member(bob)
    library.add_member(charlie)
    
    print(f"\n--- Added Members ---")
    print(f"{alice} - Max: {alice.get_max_borrow_limit()} items")
    print(f"{bob} - Max: {bob.get_max_borrow_limit()} items")
    
    # Regular member borrows items (max 3)
    print(f"\n--- Regular Member Borrowing (Max 3) ---")
    library.borrow_item(alice.member_id, book1.id)
    library.borrow_item(alice.member_id, dvd1.id)
    library.borrow_item(alice.member_id, book2.id)
    print(f"Alice borrowed: {alice.get_borrowed_count()}/{alice.get_max_borrow_limit()} items")
    
    # Try to exceed limit
    success = library.borrow_item(alice.member_id, dvd2.id)
    print(f"Alice trying 4th item: {success} (exceeded limit)")
    
    # Premium member borrows items (max 5)
    print(f"\n--- Premium Member Borrowing (Max 5) ---")
    library.borrow_item(bob.member_id, dvd2.id)
    print(f"Bob borrowed: {bob.get_borrowed_count()}/{bob.get_max_borrow_limit()} items")
    print(f"'{dvd2.title}' available: {dvd2.available_copies}")
    
    # Waiting list and Observer pattern
    print(f"\n--- Waiting List & Observer Pattern ---")
    success = library.borrow_item(charlie.member_id, dvd2.id)
    print(f"Charlie trying to borrow '{dvd2.title}': {success} (unavailable)")
    
    library.join_waiting_list(charlie.member_id, dvd2.id)
    print(f"Charlie joined waiting list")
    print(f"Waiting list size: {len(library.get_waiting_list(dvd2.id))}")
    
    # Return item - triggers notification
    print(f"\nBob returns '{dvd2.title}'...")
    library.return_item(bob.member_id, dvd2.id)
    print(f"Charlie's notifications: {charlie.get_notifications()}")
    
    # Search functionality
    print(f"\n--- Search Items ---")
    results = library.search_items("Python")
    print(f"Search 'Python': {len(results)} result(s)")
    
    results = library.search_items("Matrix")
    print(f"Search 'Matrix': {len(results)} result(s)")
    
    # Display final state
    print(f"\n--- Final State ---")
    print(f"Total items: {len(library)}")
    library.display_all_items()
    
    print("\n" + "=" * 70)
    print("DEMO COMPLETED!")
    print("=" * 70)


if __name__ == "__main__":
    main()

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Expected Output

======================================================================
LIBRARY MANAGEMENT SYSTEM - DEMO
======================================================================

--- Added Items ---
Book: Python Crash Course by Eric Matthes (ID: 1)
DVD: The Matrix by Wachowski Brothers (ID: 3)
Total items: 4

--- Polymorphism Demo: get_item_info() ---
Title: Python Crash Course
Author: Eric Matthes
ISBN: 978-1593279288
Pages: 544
Type: Book

Title: The Matrix
Director: Wachowski Brothers
Duration: 136 minutes
Genre: Sci-Fi
Type: DVD

--- Added Members ---
Alice (1) - Max: 3 items
Bob (2) - Max: 5 items

--- Regular Member Borrowing (Max 3) ---
Alice borrowed: 3/3 items
Alice trying 4th item: False (exceeded limit)

--- Premium Member Borrowing (Max 5) ---
Bob borrowed: 1/5 items
'Inception' available: 0

--- Waiting List & Observer Pattern ---
Charlie trying to borrow 'Inception': False (unavailable)
Charlie joined waiting list
Waiting list size: 1

Bob returns 'Inception'...
Charlie's notifications: ["'Inception' is now available!"]

--- Search Items ---
Search 'Python': 1 result(s)
Search 'Matrix': 1 result(s)

--- Final State ---
Total items: 4
[Display all items]

======================================================================
DEMO COMPLETED!
======================================================================

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Estimated Completion Time

1.5 - 2 hours

Deliverables

• Implementation of all 7 classes
• Demonstration of all OOP concepts
• Working sample usage code
• Proper documentation and comments