Use Python to Create a To-Do App Step-by-Step

In this step-by-step guide, you’ll build a simple terminal-based To-Do app using core Python, and by the end, you’ll understand how to expand it further with GUI or web frameworks.

Why Build a To-Do App in Python?

• It's beginner-friendly.
   
• It covers essential Python features.
   
• It's practical — you’ll use it daily.
   
• It helps you learn file operations.
   
• You can later upgrade it to a full web or desktop app.

Project Overview

We’ll build a terminal-based to-do list with the following features:

• Add a new task
   
• View all tasks
   
• Mark a task as complete
   
• Delete a task
   
• Save tasks to a file (so they persist between runs)
   

Step 1: Project Setup

You only need:

• Python (version 3.6+)
   
• A text editor (VS Code, Sublime, Notepad++)
   
• Command line or terminal
   

Create a folder:

bash

CopyEdit

mkdir todo-app

cd todo-app

Inside this folder, create a file:

bash

CopyEdit

touch todo.py

Step 2: Structure the Program

We’ll use a simple dictionary list to manage tasks. Let’s plan:

• tasks.txt to save data persistently.
   
• A list of dictionaries with task, completed fields.
   

Step 3: Load and Save Tasks

First, define how tasks will be saved and loaded from a file.

Code:

python

CopyEdit

import os

import json

FILE_NAME = “tasks.txt”

def load_tasks():

    if not os.path.exists(FILE_NAME):

        return []

    with open(FILE_NAME, 'r') as file:

        return json.load(file)

def save_tasks(tasks):

    with open(FILE_NAME, 'w') as file:

        json.dump(tasks, file, indent=4)

Explanation:

• We’re using JSON for easy read/write of task lists.
   
• tasks.txt will hold the list of tasks in JSON format.

Step 4: Display the Menu

We want to show options to the user every time they open the app.

Code:

python

CopyEdit

def show_menu():

    print("\n=== TO-DO LIST MENU ===")

    print("1. View Tasks")

    print("2. Add Task")

    print("3. Mark Task as Completed")

    print("4. Delete Task")

    print("5. Exit")

Step 5: View All Tasks

Display tasks with status.

Code:

python

CopyEdit

def view_tasks(tasks):

    if not tasks:

        print("No tasks found.")

        return

    for index, task in enumerate(tasks):

        status = "✔" if task['completed'] else "❌"

        print(f"{index + 1}. [{status}] {task['task']}")

Step 6: Add a New Task

Code:

python

CopyEdit

def add_task(tasks):

    task_name = input("Enter the task: ")

    tasks.append({'task': task_name, 'completed': False})

    save_tasks(tasks)

    print("Task added successfully!")

Step 7: Mark a Task as Completed

Code:

python

CopyEdit

def mark_completed(tasks):

    view_tasks(tasks)

    try:

        choice = int(input("Enter task number to mark as completed: ")) - 1

        if 0 <= choice < len(tasks):

            tasks[choice]['completed'] = True

            save_tasks(tasks)

            print("Task marked as completed.")

        else:

            print("Invalid task number.")

    except ValueError:

        print("Please enter a valid number.")

Step 8: Delete a Task

Code:

python

CopyEdit

def delete_task(tasks):

    view_tasks(tasks)

    try:

        choice = int(input("Enter task number to delete: ")) - 1

        if 0 <= choice < len(tasks):

            deleted = tasks.pop(choice)

            save_tasks(tasks)

            print(f"Deleted task: {deleted['task']}")

        else:

            print("Invalid task number.")

    except ValueError:

        print("Please enter a valid number.")

Step 9: Main App Loop

Now that we have all the building blocks, let’s combine them into a loop.

Code:

python

CopyEdit

def main():

    tasks = load_tasks()

    while True:

        show_menu()

        choice = input("Choose an option (1-5): ")

        if choice == '1':

            view_tasks(tasks)

        elif choice == '2':

            add_task(tasks)

        elif choice == '3':

            mark_completed(tasks)

        elif choice == '4':

            delete_task(tasks)

        elif choice == '5':

            print("Exiting... Have a productive day!")

            break

        else:

            print("Invalid choice. Try again.")         

if __name__ == "__main__":

    main()

Sample Output:

vbnet

CopyEdit

=== TO-DO LIST MENU ===

1. View Tasks

2. Add Task

3. Mark Task as Completed

4. Delete Task

5. Exit

Choose an option (1-5): 2

Enter the task: Complete Python project

Task added successfully!

=== TO-DO LIST MENU ===

1. View Tasks

…

How It Works Behind the Scenes

• tasks.txt is used to persist data using JSON.
   
• A list of dictionaries stores each task with its status.
   
• Every time the user performs an operation, the file is updated.

Ideas to Upgrade This App

Once you understand this terminal version, here are upgrade ideas:

1. Add Due Dates

Add a due_date field to tasks:

python

CopyEdit

tasks.append({'task': task_name, 'completed': False, 'due_date': '2026-08-05'})

2. Use a GUI Framework

Use Tkinter or PyQt to make a desktop app with buttons and checkboxes.

3. Use a Database

Use SQLite to store tasks instead of a text file.

4. Convert It to a Web App

Use Flask or Django to convert this into a fully working web app.

Why This Project Is Great for Beginners

Frequently Asked Questions

Q: Can I make this app in other languages?

Yes, you can build the same app using JavaScript (Node.js), C++, Java, or any language that supports I/O and logic control.

Q: How to run this app repeatedly?

Just run:

bash

CopyEdit

python todo.py

The tasks are saved between sessions using the tasks.txt file.

Q: How to make it available on my phone or online?

You can use Flask to create a web version and host it on platforms like Render, PythonAnywhere, or Heroku.

Final Thoughts

Building a simple To-Do app in Python is more than just writing code. It’s your gateway into learning how real applications work — from user input to data storage. By following this project, you've already used file I/O, data structures, loops, and conditional logic.

This small but powerful project is the perfect foundation for larger apps in the future.

Ready to Build More Real-World Projects?

👉 Learn Python with real hands-on projects at Uncodemy. Their Python Programming Course covers beginner to advanced concepts with live classes, mentorship, and career support.

Take your skills from simple scripts to full applications — start learning today.