Building Your First Web App with Flask: A Simple To-Do List Example

[Tutorial] · 2026-01-15 03:11 UTC

Building Your First Web App with Flask: A Simple To-Do List Example

💡 TL;DR

Learn how to create a simple web app with Flask by building a “To-Do List” example using code examples.

📚 Learning Objectives

This tutorial teaches beginners how to build a basic web application using Flask, a popular Python framework for creating dynamic websites. We’ll cover the fundamentals of Flask, including setting up an environment and creating a simple to-do list app.

🎯 Key Concepts

Introduction to Flask
Setting Up Your Environment
Building the To-Do List App
User Interaction and Data Storage

Concept Explanation

Flask is a lightweight web framework that allows you to build web applications in Python. It’s renowned for its simplicity, allowing developers to focus on creating dynamic and interactive content without getting bogged down by complex code structures.
In this tutorial, we’ll be using Flask to construct a basic To-Do list application, providing users with the ability to add tasks, view their existing lists, and potentially even complete them.

Code Example 1: Basic To-Do List App

from flask import Flask, render_template

app = Flask(__name__)

@app.route('/')
def index():
tasks = [
{'id': 1, 'task': 'Learn Flask', 'done': False},
{'id': 2, 'task': 'Build a To-Do App', 'done': True}
]
return render_template('index.html', tasks=tasks)

if __name__ == '__main__':
app.run(debug=True)

Execution Result

Running this code creates a simple web server that displays the tasks in your browser. You can use a tool like flask run or python app.py to start and view the results. flask run``python app.py

Code Example 2: Adding Tasks

from flask import Flask, render_template, request

app = Flask(__name__)

@app.route('/')
def index():
return render_template('index.html')

@app.route('/add', methods=['POST'])
def add_task():
new_task = request.form['task']
tasks.append({'id': len(tasks) + 1, 'task': new_task, 'done': False}) return render_template('index.html', tasks=tasks)

if __name__ == '__main__':
app.run(debug=True)

Execution Result

This example shows how to add a new task to your To-Do list.

Tips & Best Practices

For production environments, you can use databases like SQL or NoSQL to store and manage data more efficiently.
Explore different ways of displaying the tasks on the frontend using frameworks such as Bootstrap or Tailwind CSS.
Implement error handling, validation, and security measures in your application for a robust user experience.

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Building Your First Web App with Flask: A Simple To-Do List Example