To-Do List CLI App

📝 To-Do List CLI App

🎮 What We're Building

A command-line to-do list: add tasks, list them, mark them done, and have the list still be there the next time you run the program — all stored in a plain JSON file.

Step 1: Representing a Task as a Dict

Copytask = {"title": "Buy milk", "done": False}
tasks = [task]

No class needed — a task is just a dict (Course 1, Chapter 7) with two keys, and the whole to-do list is a plain list of these dicts. This is the direct "no heavy OOP required" alternative to py3-8's Task dataclass — less structure, but perfectly workable for a project this size.

Step 2: Loading and Saving with JSON

Copyimport json
from pathlib import Path

FILE = Path("tasks.json")

def load_tasks():
    if not FILE.exists():
        return []
    return json.loads(FILE.read_text())

def save_tasks(tasks):
    FILE.write_text(json.dumps(tasks, indent=2))

pathlib and json here work exactly like Course 2, Chapters 4 and 7 — but note there's no separate Task class to reconstruct on load, unlike py3-8's Task(**item) step. json.loads() already returns plain dicts, which is exactly what this version's tasks list is made of — one less layer, at the cost of losing the type-checking and auto-generated __eq__ a dataclass would give.

Step 3: Adding, Listing, Completing Tasks

Copydef add_task(tasks, title):
    tasks.append({"title": title, "done": False})

def list_tasks(tasks):
    if not tasks:
        print("No tasks yet!")
        return
    for i, task in enumerate(tasks, start=1):
        status = "x" if task["done"] else " "
        print(f"{i}. [{status}] {task['title']}")

def complete_task(tasks, index):
    if 0 <= index < len(tasks):
        tasks[index]["done"] = True
    else:
        print("Invalid task number.")

enumerate(tasks, start=1) reuses Course 1, Chapter 4's numbered-list pattern for a human-friendly 1-based display. complete_task mutates the dict directly through its list position — tasks[index]["done"] = True — since tasks.append() is passed the same list object every function receives (Course 1's mutable-list-aliasing behavior, here working in the app's favor).

Step 4: The Menu Loop

Copytasks = load_tasks()

while True:
    print("\n1. Add  2. List  3. Complete  4. Quit")
    choice = input("Choose an option: ")

    if choice == "1":
        title = input("Task title: ")
        add_task(tasks, title)
        save_tasks(tasks)
    elif choice == "2":
        list_tasks(tasks)
    elif choice == "3":
        num = int(input("Task number to complete: "))
        complete_task(tasks, num - 1)
        save_tasks(tasks)
    elif choice == "4":
        print("Goodbye!")
        break
    else:
        print("Not a valid option, try again.")

Same menu-loop shape as Chapters 1 and 2. save_tasks(tasks) is called after every mutation (add, complete) — skip it and the change would only exist in memory for this run, lost the moment the program exits, undermining the whole point of persistence.

🏁 The Complete To-Do App

Copyimport json
from pathlib import Path

FILE = Path("tasks.json")

def load_tasks():
    if not FILE.exists():
        return []
    return json.loads(FILE.read_text())

def save_tasks(tasks):
    FILE.write_text(json.dumps(tasks, indent=2))

def add_task(tasks, title):
    tasks.append({"title": title, "done": False})

def list_tasks(tasks):
    if not tasks:
        print("No tasks yet!")
        return
    for i, task in enumerate(tasks, start=1):
        status = "x" if task["done"] else " "
        print(f"{i}. [{status}] {task['title']}")

def complete_task(tasks, index):
    if 0 <= index < len(tasks):
        tasks[index]["done"] = True
    else:
        print("Invalid task number.")

tasks = load_tasks()

while True:
    print("\n1. Add  2. List  3. Complete  4. Quit")
    choice = input("Choose an option: ")

    if choice == "1":
        title = input("Task title: ")
        add_task(tasks, title)
        save_tasks(tasks)
    elif choice == "2":
        list_tasks(tasks)
    elif choice == "3":
        num = int(input("Task number to complete: "))
        complete_task(tasks, num - 1)
        save_tasks(tasks)
    elif choice == "4":
        print("Goodbye!")
        break
    else:
        print("Not a valid option, try again.")

🎯 What's Next

Next chapter: Quiz Game — dictionaries, lists, and scoring logic.