📚 Simple Library Management System

This is a beginner-friendly project made with Python in Jupyter Notebook. It helps you practice using:

• ✅ Lists
• ✅ Tuples
• ✅ Sets
• ✅ Dictionaries
• ✅ Nested data (like a list inside a dictionary)

---

🎯 What This Project Does

You’ll build a small system to:

1. Store book info like title and author
2. Track users and which books they borrowed
3. Show available books
4. Let users borrow or return books
5. Learn core Python data types

---

🛠️ What You’ll Learn

Python Concept	What You’ll Use It For
List	To track borrowed books
Tuple	To store book details (title, author)
Set	To collect unique genres
Dictionary	To store books and user info
Nested data	A dictionary with lists or tuples

---

📋 Steps in the Notebook

1. Create a book list using a dictionary:

books = {
  "B001": ("The Alchemist", "Paulo Coelho", "Fiction"),
  "B002": ("1984", "George Orwell", "Dystopian")
}

2. Track users and what they borrowed:

users = {
  "alice": ["B001"],
  "bob": []
}

3. Get unique genres using a set:

genres = set(book[2] for book in books.values())

4. Make simple functions:

• View all books
• Borrow a book
• Return a book

5. Add a menu using a while loop:

while True:
    print("1. View Books\n2. Borrow\n3. Return\n4. Exit")
    choice = input("Choose an option: ")

📚 Welcome to Davina's Library Code Walkthrough

This Python program simulates a small library system. It organizes a collection of books by their genres and displays them in an easy-to-read format.

---

🏷️ Library Name

library = "Davina's Library"
print(f"=== Welcome to {library} ===")

We start by setting the name of the library and printing a welcome message. The {library} part gets replaced with the actual name.

---

📖 Book Collection

books = {
    "B001": ("The Alchemist", "Paulo Coelho", "Fiction"),
    ...
}

• This is a dictionary where each book has a unique ID like "B001".
• Each book's value is a tuple containing:
  • The title of the book
  • The author’s name
  • The genre it belongs to

Think of it like a library record card for each book.

---

🗂️ Genres

genres = {
    "Fiction",
    "Dystopian",
    ...
}

This is a set of all the different book genres. Sets are used when we only want unique values (no duplicates).

---

🧩 Grouping Books by Genre

books_by_genre = {}

We create an empty dictionary to store books sorted by genre.

---

🔄 Looping Through the Books

for book_id, (title, author, genre) in books.items():
    if genre not in books_by_genre:
        books_by_genre[genre] = []
    books_by_genre[genre].append(book_id)

• This loop checks each book’s genre.
• If the genre isn’t in the dictionary yet, it creates a new list for that genre.
• Then, it adds the book ID to the list under the correct genre.

---

📋 Displaying the Books

for genre, book_uuids in books_by_genre.items():
    print(f"\n📚 Genre: {genre}")
    for book_uuid in book_uuids:
        title, author, _ = books[book_uuid]
        print(f"  - {book_uuid}: {title} by {author}")

This section prints each genre followed by a list of books under that category, including their:

• Book ID
• Title
• Author

---

✅ Example Output

📚 Genre: Fiction
  - B001: The Alchemist by Paulo Coelho

📚 Genre: Classic
  - B003: To Kill a Mockingbird by Harper Lee
  - B004: The Great Gatsby by F. Scott Fitzgerald

---

💡 Summary

This code teaches:

• How to store and access book info using dictionaries and tuples
• How to avoid duplicate genres using a set
• How to organize data using loops and nested structures

Perfect for beginners building a simple but structured Python project!

library = "Davina's Library"
print(f"=== Welcome to {library} ===")

# books data structure > dictionary { book uuid }
# book item data structure > tuple: (title, author, genre)
books = {
    "B001": ("The Alchemist", "Paulo Coelho", "Fiction"),
    "B002": ("1984", "George Orwell", "Dystopian"),
    "B003": ("To Kill a Mockingbird", "Harper Lee", "Classic"),
    "B004": ("The Great Gatsby", "F. Scott Fitzgerald", "Classic"),
    "B005": ("Sapiens", "Yuval Noah Harari", "Non-fiction"),
    "B006": ("Python Crash Course", "Eric Matthes", "Programming"),
    "B007": ("The Hobbit", "J.R.R. Tolkien", "Fantasy"),
    "B008": ("A Brief History of Time", "Stephen Hawking", "Science"),
    "B009": ("Becoming", "Michelle Obama", "Biography"),
    "B010": ("The Silent Patient", "Alex Michaelides", "Thriller")
}

# genres data structure > dictionary { genre name }
genres = {
    "Fiction",
    "Dystopian",
    "Classic",
    "Non-fiction",
    "Programming",
    "Fantasy",
    "Science",
    "Biography",
    "Thriller"
}

# books_by_genre > dictionary { book uuid }
books_by_genre = {}

print("--- Books Sorted by Genre ---")
for book_id, (title, author, genre) in books.items():
    if genre not in books_by_genre:
        books_by_genre[genre] = []
    books_by_genre[genre].append(book_id)

for genre, book_uuids in books_by_genre.items():
    print(f"\n📚 Genre: {genre}")
    for book_uuid in book_uuids:
        title, author, _ = books[book_uuid]
        print(f"  - {book_uuid}: {title} by {author}")

=== Welcome to Davina's Library ===
--- Books Sorted by Genre ---

📚 Genre: Fiction
  - B001: The Alchemist by Paulo Coelho

📚 Genre: Dystopian
  - B002: 1984 by George Orwell

📚 Genre: Classic
  - B003: To Kill a Mockingbird by Harper Lee
  - B004: The Great Gatsby by F. Scott Fitzgerald

📚 Genre: Non-fiction
  - B005: Sapiens by Yuval Noah Harari

📚 Genre: Programming
  - B006: Python Crash Course by Eric Matthes

📚 Genre: Fantasy
  - B007: The Hobbit by J.R.R. Tolkien

📚 Genre: Science
  - B008: A Brief History of Time by Stephen Hawking

📚 Genre: Biography
  - B009: Becoming by Michelle Obama

📚 Genre: Thriller
  - B010: The Silent Patient by Alex Michaelides

👤 User Management in Davina's Library

This section of the Python program manages the library users and shows what books they've borrowed. It interacts with users by asking for their name and displaying their borrowed books if they're registered.

---

📇 User Data

users = {
    "alice": ["B001", "B005"],
    "bob": [],
    "charlie": ["B007"],
    "diana": ["B003", "B010"],
    "ethan": ["B006"]
}

• This is a dictionary where each key is a user name.
• Each user has a list of book IDs they’ve borrowed.
• If the list is empty ([]), the user hasn't borrowed any books yet.

Think of it like each user has a folder with a list of borrowed book IDs inside.

---

👀 Show All Users

print(f"--- Users of {library} ---")
for user in users:
    print(f"- {user}")

• Prints out a list of all users in the system.
• Helpful for testing or verifying who is registered.

---

🧾 User Login and Borrowed Books Check

user = input("Please enter your name:")
user_input = str(user).lower()

• Asks the user to type their name.
• Converts the name to lowercase so the check is case-insensitive (e.g., Alice = alice).

---

✅ If the User Exists

if user_input in users:
    print(f"Welcome back, {user}:")

• Checks if the entered name is already in the users dictionary.

---

📚 Show Borrowed Books

borrowed_book_uuids = users[user_input]

if borrowed_book_uuids:
    print("You have borrowed the following books:")

    for borrowed_book_uuid in borrowed_book_uuids:
        (title, author, genre) = books[borrowed_book_uuid]
        print(f"  - {borrowed_book_uuid}: {title} by {author}, {genre}")

• Retrieves the list of book IDs the user has borrowed.
• For each book ID, it looks up the book title, author, and genre from the books dictionary.
• Prints the full book info in a friendly format.

---

❌ If the User is Not Found

else:
    print(f"User '{user}' not found. Please register first.")

• This message is shown when someone who isn't in the system tries to log in.

---

💡 Summary

This code helps beginners understand:

Concept	Purpose
dict	To store users and what they’ve borrowed
list	To keep track of each user’s borrowed books
input()	To get the user’s name
for loop	To print lists of users and books
if statement	To check if the user exists and what they borrowed

# users data structure > dictionary { user name }
# user item data structure > list: [book uuid]
users = {
    "alice": ["B001", "B005"],          # Borrowed: The Alchemist, Sapiens
    "bob": [],                          # No borrowed books
    "charlie": ["B007"],               # Borrowed: The Hobbit
    "diana": ["B003", "B010"],         # Borrowed: To Kill a Mockingbird, The Silent Patient
    "ethan": ["B006"]                  # Borrowed: Python Crash Course
}

# Print out the users of the library management system
print(f"--- Users of {library} ---")
for user in users:
    print(f"- {user}")

user = input("Please enter your name:")
user_input = str(user).lower()

if user_input in users:
    print(f"Welcome back, {user}:")

    borrowed_book_uuids = users[user_input]

    if borrowed_book_uuids:
        print("You have borrowed the following books:")

        for borrowed_book_uuid in borrowed_book_uuids:
            (title, author, genre) = books[borrowed_book_uuid]
            print(f"  - {borrowed_book_uuid}: {title} by {author}, {genre}")
else:
    print(f"User '{user}' not found. Please register first.")

--- Users of Davina's Library ---
- alice
- bob
- charlie
- diana
- ethan

Welcome back, Alice:
You have borrowed the following books:
  - B001: The Alchemist by Paulo Coelho, Fiction
  - B005: Sapiens by Yuval Noah Harari, Non-fiction

🔁 Borrow & Return System — Davina's Library

This part of the program allows registered users to borrow or return books using simple commands. It includes a basic menu and checks to ensure everything is valid.

---

🖥️ System Startup

print(f"--- {library} Borrow/Return System ---")

• Displays a title for the borrow/return section of the system.
• {library} refers to the library name you set earlier.

---

🧾 Available Actions

actions = ("borrow", "return")

• A tuple that defines two options: "borrow" or "return".
• These options are used later to decide what the user wants to do.

---

👤 Ask for User Name

user = input("Please enter your name:")
user_input = str(user).lower()

• Gets the user’s name as input.
• Converts the name to lowercase so it matches stored names regardless of capitalization.

---

🔐 Check If User Is Registered

if user_input in users:

• Looks for the user in the system.
• If the user exists, they can continue to borrow or return books.

---

🧭 Choose an Action

print(f"Available options: {actions}")
action = input("Please enter your choice (borrow/return): ").lower()

• Displays available actions.
• Asks the user what they want to do.

---

📚 If the User Chooses to Borrow

if action == actions[0]:

• Shows books grouped by genre.
• Each book is displayed with its ID, title, and author.

book_uuid = input("Which book would you like to borrow?")

• Asks for the book’s ID.

if book_uuid in books and book_uuid not in users[user_input]:
    users[user_input].append(book_uuid)
    ...

• Confirms the book exists and isn’t already borrowed by the user.
• Adds the book to the user’s list of borrowed books.

---

📤 If the User Chooses to Return

elif action == actions[1]:

• Lists all books the user has borrowed.

book_uuid = input("Which book would you like to return?")

• Asks which book the user wants to return.

if book_uuid in borrowed_book_uuids:
    borrowed_book_uuids.remove(book_uuid)

• Removes the returned book from the user’s borrowed list.

---

🛑 Error Handling

else:
    print(f"Invalid action '{action}'.")

• Shows an error if the user types anything other than "borrow" or "return".

else:
    print(f"User '{user}' not found. Please register first.")

• If the user isn’t in the system, it prompts them to register.

---

💡 Summary

This code demonstrates: | Concept | What It Does | |-----------------|-----------------------------------------------------------| | tuple | Stores fixed choices (borrow, return) | | input() | Gets information from the user | | if/else | Controls the flow based on user input | | list | Tracks books each user has borrowed | | dictionary | Matches users and book IDs | | loop | Displays multiple books neatly |

print(f"--- {library} Borrow/Return System ---")

# actions data structure > tuple
actions = ("borrow", "return")

user = input("Please enter your name:")
user_input = str(user).lower()

if user_input in users:
    user = users[user_input]

    print(f"Would you like to borrow or return a book?")
    print(f"Available options: {actions}")
    action = input("Please enter your choice (borrow/return): ").lower()

    # if user wants to borrow a book
    if action == actions[0]:
        print("Available books:")
        
        for genre, book_uuids in books_by_genre.items():
            print(f"\n📚 Genre: {genre}")
            for book_uuid in book_uuids:
                title, author, _ = books[book_uuid]
                print(f"  - {book_uuid}: {title} by {author}")

        book_uuid = input("Which book would you like to borrow?").upper()

        if book_uuid in books and book_uuid not in users[user_input]:
            users[user_input].append(book_uuid)

            title, author, genre = books[book_uuid]
            print(f"You borrowed '{book_uuid}: {title} by {author}, {genre}'")
        else:
            print(f"Book '{book_uuid}' not found.")
      
    # if user wants to return a book
    elif action == actions[1]:
        borrowed_book_uuids = users[user_input]
    
        if borrowed_book_uuids:
            print("You have borrowed the following books:")
    
            for borrowed_book_uuid in borrowed_book_uuids:
                (title, author, genre) = books[borrowed_book_uuid]
                print(f"  - {borrowed_book_uuid}: {title} by {author}, {genre}")

            book_uuid = input("Which book would you like to return?").upper()

            if book_uuid in borrowed_book_uuids:
                borrowed_book_uuids.remove(book_uuid)
                users[user_input] = borrowed_book_uuids
                (title, author, genre) = books[book_uuid]
                print(f"You returned: '{book_uuid}: {title} by {author}, {genre}")

                if borrowed_book_uuids:
                    print("You have following books left:")
        
                    for borrowed_book_uuid in borrowed_book_uuids:
                        (title, author, genre) = books[borrowed_book_uuid]
                        print(f"  - {borrowed_book_uuid}: {title} by {author}, {genre}")
            else:
                print(f"Book '{book_uuid}' not found.")
        else:
            print("You haven't borrowed any books yet.")
    else:
        print(f"Invalid action '{action}'.")
else:
    print(f"User '{user}' not found. Please register first.")

--- Davina's Library Borrow/Return System ---

Would you like to borrow or return a book?
Available options: ('borrow', 'return')

You have borrowed the following books:
  - B006: Python Crash Course by Eric Matthes, Programming

You returned: 'B006: Python Crash Course by Eric Matthes, Programming

# 📚 Davina's Library System (Python CLI App)

This is a simple, text-based **Library Management System** written in Python. Users can borrow and return books using the command line. This project is ideal for beginners who want to learn about Python data types and control flow.

---

## ✨ Features

- 📖 View all books grouped by genre
- 👤 View a list of registered users
- 🔐 Log in using your name
- ✅ See what books you've borrowed
- 📚 Borrow a book (if not already borrowed)
- 📤 Return a borrowed book

---

## 🧱 How It Works

### 1. 📘 Book Data
Books are stored using a **dictionary**. Each book has a unique ID (like `B001`) and contains:
- Title
- Author
- Genre

Example:
```python
books = {
    "B001": ("The Alchemist", "Paulo Coelho", "Fiction")
}
```

---

### 2. 🎨 Genres
Genres are stored in a **set**:
```python
genres = {
    "Fiction", "Dystopian", "Classic", ...
}
```
This ensures no duplicates and makes it easy to organize books.

---

### 3. 🗂️ Books by Genre
Books are grouped into genres using a dictionary called `books_by_genre`:
```python
books_by_genre = {
    "Fiction": ["B001", "B004"],
    ...
}
```

This is printed in a friendly format so users can browse all books.

---

### 4. 👥 User Data
Each user is stored in a **dictionary** with their name as the key and a list of borrowed book IDs as the value.

Example:
```python
users = {
    "alice": ["B001", "B005"],
    "bob": []
}
```

---

## 🔁 Main Interactions

After listing books and users:

### Step 1: Login
The program asks you to enter your name. If you’re registered, it welcomes you and shows your borrowed books.

### Step 2: Borrow or Return
You’re asked whether you want to `"borrow"` or `"return"` a book.

### Step 3A: Borrowing
- All available books are shown grouped by genre.
- You type the book ID you want to borrow.
- If it’s valid and not already borrowed, the book is added to your list.

### Step 3B: Returning
- Your borrowed books are displayed.
- You choose a book ID to return.
- If valid, the book is removed from your list and a confirmation is shown.

---

## ⚠️ Error Handling

The program handles:
- Users not found (asks them to register)
- Invalid book IDs
- Trying to borrow a book already borrowed
- Trying to return a book not currently borrowed

---

## 🧠 Concepts Practiced

| Python Concept | Usage                                |
|----------------|---------------------------------------|
| `dict`         | Storing books, users, and genres      |
| `list`         | Tracking borrowed books per user      |
| `tuple`        | Storing book details                  |
| `set`          | Managing unique genres                |
| `input()`      | Accepting user interaction            |
| `if/else`      | Making decisions based on conditions  |
| `for` loop     | Printing books and user lists         |
| `str.lower()`  | Handling case-insensitive names       |

---

## 🚀 How to Run

1. Open the code in a Python IDE or Jupyter Notebook.
2. Run the script.
3. Follow the on-screen prompts.

---

## 🔧 Ideas for Expansion

- Add registration for new users
- Save and load data using JSON files
- Track number of available copies per book
- Add due dates and overdue notices

---

👩‍💻 Happy coding and borrowing!

# === Davina's Library System ===
library = "Davina's Library"
print(f"=== Welcome to {library} ===")

# Book database: book_id => (title, author, genre)
books = {
    "B001": ("The Alchemist", "Paulo Coelho", "Fiction"),
    "B002": ("1984", "George Orwell", "Dystopian"),
    "B003": ("To Kill a Mockingbird", "Harper Lee", "Classic"),
    "B004": ("The Great Gatsby", "F. Scott Fitzgerald", "Classic"),
    "B005": ("Sapiens", "Yuval Noah Harari", "Non-fiction"),
    "B006": ("Python Crash Course", "Eric Matthes", "Programming"),
    "B007": ("The Hobbit", "J.R.R. Tolkien", "Fantasy"),
    "B008": ("A Brief History of Time", "Stephen Hawking", "Science"),
    "B009": ("Becoming", "Michelle Obama", "Biography"),
    "B010": ("The Silent Patient", "Alex Michaelides", "Thriller")
}

# Users and their borrowed book IDs
users = {
    "alice": ["B001", "B005"],
    "bob": [],
    "charlie": ["B007"],
    "diana": ["B003", "B010"],
    "ethan": ["B006"]
}

# Group books by genre
books_by_genre = {}
for book_id, (_, _, genre) in books.items():
    books_by_genre.setdefault(genre, []).append(book_id)

# Show all books grouped by genre
def show_all_books():
    print("\n--- Books Sorted by Genre ---")
    for genre, book_ids in books_by_genre.items():
        print(f"\n📚 {genre}")
        for book_id in book_ids:
            title, author, _ = books[book_id]
            print(f"  - {book_id}: {title} by {author}")

# Show a user's borrowed books
def show_borrowed_books(username):
    borrowed = users[username]
    if not borrowed:
        print("You haven't borrowed any books yet.")
    else:
        print("You have borrowed the following books:")
        for book_id in borrowed:
            title, author, genre = books[book_id]
            print(f"  - {book_id}: {title} by {author}, {genre}")

# Borrow a book
def borrow_book(username):
    show_all_books()
    book_id = input("\nWhich book would you like to borrow? ").upper()
    if book_id not in books:
        print("That book ID does not exist.")
    elif book_id in users[username]:
        print("You've already borrowed this book.")
    else:
        users[username].append(book_id)
        title, author, genre = books[book_id]
        print(f"You borrowed: {book_id}: {title} by {author} ({genre})")

# Return a book
def return_book(username):
    borrowed = users[username]
    if not borrowed:
        print("You haven't borrowed any books yet.")
        return

    show_borrowed_books(username)
    book_id = input("\nWhich book would you like to return? ").upper()
    if book_id in borrowed:
        borrowed.remove(book_id)
        title, author, genre = books[book_id]
        print(f"You returned: {book_id}: {title} by {author} ({genre})")
    else:
        print("You haven't borrowed that book.")

# === Start Program ===

# Show registered users
print("\n--- Registered Users ---")
for name in users:
    print(f"- {name}")

# Login
username_input = input("\nPlease enter your name: ").strip().lower()

if username_input in users:
    print(f"\nWelcome back, {username_input.capitalize()}!")
    show_borrowed_books(username_input)

    action = input("\nWould you like to borrow or return a book? (borrow/return): ").lower()
    if action == "borrow":
        borrow_book(username_input)
    elif action == "return":
        return_book(username_input)
    else:
        print("Invalid action. Please type 'borrow' or 'return'.")
else:
    print(f"User '{username_input}' not found. Please register first.")

=== Welcome to Davina's Library ===

--- Registered Users ---
- alice
- bob
- charlie
- diana
- ethan

Welcome back, Alice!
You have borrowed the following books:
  - B001: The Alchemist by Paulo Coelho, Fiction
  - B005: Sapiens by Yuval Noah Harari, Non-fiction

You have borrowed the following books:
  - B001: The Alchemist by Paulo Coelho, Fiction
  - B005: Sapiens by Yuval Noah Harari, Non-fiction

You returned: B001: The Alchemist by Paulo Coelho (Fiction)

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