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