Putting It All Together: Mini Projects

Congratulations — you have learned all the fundamental building blocks of Python! Now it is time to combine everything into real, working programs. In this final lesson, you will build three mini projects that use variables, data types, strings, control flow, loops, lists, dictionaries, functions, file handling, and exception handling.

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Project 1: Contact Book

A command-line application that lets you add, search, list, and delete contacts, with data saved to a JSON file.

import json
import os

CONTACTS_FILE = "contacts.json"

def load_contacts() -> list[dict]:
    """Load contacts from the JSON file."""
    if not os.path.exists(CONTACTS_FILE):
        return []
    try:
        with open(CONTACTS_FILE, "r") as f:
            return json.load(f)
    except (json.JSONDecodeError, IOError):
        print("Warning: Could not read contacts file. Starting fresh.")
        return []

def save_contacts(contacts: list[dict]) -> None:
    """Save contacts to the JSON file."""
    with open(CONTACTS_FILE, "w") as f:
        json.dump(contacts, f, indent=2)

def add_contact(contacts: list[dict]) -> None:
    """Add a new contact."""
    name = input("Name: ").strip()
    if not name:
        print("Name cannot be empty.")
        return

    phone = input("Phone: ").strip()
    email = input("Email: ").strip()

    # Check for duplicates
    for contact in contacts:
        if contact["name"].lower() == name.lower():
            print(f"A contact named '{name}' already exists.")
            return

    contacts.append({
        "name": name,
        "phone": phone,
        "email": email
    })
    save_contacts(contacts)
    print(f"Contact '{name}' added successfully!")

def search_contacts(contacts: list[dict]) -> None:
    """Search contacts by name."""
    query = input("Search: ").strip().lower()
    results = [c for c in contacts if query in c["name"].lower()]

    if results:
        print(f"\nFound {len(results)} result(s):")
        for c in results:
            print(f"  Name: {c['name']}")
            print(f"  Phone: {c['phone']}")
            print(f"  Email: {c['email']}")
            print()
    else:
        print("No contacts found.")

def list_contacts(contacts: list[dict]) -> None:
    """List all contacts."""
    if not contacts:
        print("No contacts yet.")
        return

    print(f"\n{'Name':<20} {'Phone':<15} {'Email'}")
    print("-" * 55)
    for c in sorted(contacts, key=lambda x: x["name"]):
        print(f"{c['name']:<20} {c['phone']:<15} {c['email']}")

def delete_contact(contacts: list[dict]) -> None:
    """Delete a contact by name."""
    name = input("Name to delete: ").strip()
    for i, c in enumerate(contacts):
        if c["name"].lower() == name.lower():
            contacts.pop(i)
            save_contacts(contacts)
            print(f"Deleted '{name}'.")
            return
    print(f"Contact '{name}' not found.")

def main():
    """Main application loop."""
    contacts = load_contacts()
    print("Contact Book")
    print("=" * 30)

    while True:
        print("\nOptions: [a]dd  [s]earch  [l]ist  [d]elete  [q]uit")
        choice = input("> ").strip().lower()

        if choice == "a":
            add_contact(contacts)
        elif choice == "s":
            search_contacts(contacts)
        elif choice == "l":
            list_contacts(contacts)
        elif choice == "d":
            delete_contact(contacts)
        elif choice == "q":
            print("Goodbye!")
            break
        else:
            print("Invalid option. Try again.")

if __name__ == "__main__":
    main()

What This Project Uses

• Functions — each action is a separate function
• Lists and dictionaries — contacts stored as a list of dicts
• File handling — JSON persistence
• Exception handling — safe file reading
• Loops — main application loop with while True
• Control flow — menu selection with if/elif/else
• String methods — .strip(), .lower() for input handling

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Project 2: Quiz Game

A multiple-choice quiz with scoring, loaded from a dictionary:

import random

def create_quiz() -> list[dict]:
    """Define quiz questions."""
    return [
        {
            "question": "What is the output of print(type(42))?",
            "options": ["<class 'int'>", "<class 'float'>", "<class 'str'>", "<class 'number'>"],
            "answer": 0
        },
        {
            "question": "Which method removes the last element from a list?",
            "options": ["remove()", "delete()", "pop()", "discard()"],
            "answer": 2
        },
        {
            "question": "What does 'len' stand for?",
            "options": ["Length", "Lenient", "Lend", "Lengthy"],
            "answer": 0
        },
        {
            "question": "Which keyword defines a function in Python?",
            "options": ["func", "function", "def", "define"],
            "answer": 2
        },
        {
            "question": "What is the result of 10 // 3?",
            "options": ["3.33", "3", "4", "3.0"],
            "answer": 1
        },
        {
            "question": "Which data type is immutable?",
            "options": ["list", "dict", "set", "tuple"],
            "answer": 3
        },
        {
            "question": "What does the 'in' keyword do?",
            "options": [
                "Creates a variable",
                "Tests membership in a sequence",
                "Imports a module",
                "Defines a loop"
            ],
            "answer": 1
        },
        {
            "question": "What is the output of bool('')?",
            "options": ["True", "False", "None", "Error"],
            "answer": 1
        },
    ]

def run_quiz(questions: list[dict]) -> tuple[int, int]:
    """Run the quiz and return (correct, total)."""
    random.shuffle(questions)
    correct = 0
    total = len(questions)

    for i, q in enumerate(questions, 1):
        print(f"\nQuestion {i}/{total}: {q['question']}")
        for j, option in enumerate(q["options"]):
            print(f"  {j + 1}. {option}")

        while True:
            try:
                answer = int(input("Your answer (1-4): ")) - 1
                if 0 <= answer <= 3:
                    break
                print("Please enter 1, 2, 3, or 4.")
            except ValueError:
                print("Please enter a number.")

        if answer == q["answer"]:
            print("Correct!")
            correct += 1
        else:
            print(f"Wrong! The answer was: {q['options'][q['answer']]}")

    return correct, total

def main():
    print("Python Quiz Game")
    print("=" * 30)

    questions = create_quiz()
    correct, total = run_quiz(questions)

    percentage = (correct / total) * 100
    print(f"\nResults: {correct}/{total} ({percentage:.0f}%)")

    if percentage == 100:
        print("Perfect score!")
    elif percentage >= 70:
        print("Great job!")
    elif percentage >= 50:
        print("Not bad — keep practising!")
    else:
        print("Keep learning — you'll get there!")

if __name__ == "__main__":
    main()

What This Project Uses