📘 Lesson 29 · Advanced

Project: Python To-Do App

Build a to-do app with add, complete, delete, and JSON persistence.

Project Overview

This project builds a command-line to-do list manager. Tasks are saved to a JSON file so they persist between sessions — closing the program doesn't lose your data. The project shows how different concepts combine in a real app: data structures, file I/O, functions, and user interaction.

💡

Concepts: lists, dicts, JSON, file I/O, functions, while loop, enumerate, os.path.

Data Structure and Storage

Each task is a dictionary with a title and a done boolean. All tasks live in a list. The load/save functions use JSON so data persists between runs. os.path.exists() prevents a crash when the file hasn't been created yet.

storage.py

import json, os
FILE = "tasks.json"

def load_tasks():
    if os.path.exists(FILE):
        with open(FILE) as f: return json.load(f)
    return []

def save_tasks(tasks):
    with open(FILE, "w") as f: json.dump(tasks, f, indent=2)

▶ Output

(Helper functions — no output)

Task Operations

ops.py

def show(tasks):
    if not tasks: print("  No tasks."); return
    for i, t in enumerate(tasks, 1):
        icon = "✓" if t["done"] else "○"
        print(f"  {i}. [{icon}] {t['title']}")

def add(tasks, title):
    tasks.append({{"title": title, "done": False}})
    save_tasks(tasks); print(f"Added: {title}")

def complete(tasks, i):
    tasks[i]["done"] = True
    save_tasks(tasks); print(f"Done: {tasks[i]['title']}")

# Demo
t = []
add(t, "Buy groceries")
add(t, "Read Python docs")
complete(t, 0)
show(t)

▶ Output

Added: Buy groceries
Added: Read Python docs
Done: Buy groceries
  1. [✓] Buy groceries
  2. [○] Read Python docs

✅

Extend this with priority levels, due dates, or categories — then build a GUI version with tkinter once you're comfortable.

🧠 Quick Check

Which built-in gives both index and value while looping?

range()

zip()

enumerate()

map()