3 Practical Examples of Creating a Basic Flask Application

Introduction to Flask Applications

Flask is a lightweight web framework for Python that makes it easy to build web applications quickly and with minimal setup. It’s great for beginners because of its simplicity and flexibility. In this guide, we’ll walk through three diverse examples of creating a basic Flask application, each demonstrating different concepts and use cases.

Example 1: Hello, World! Flask Application

Context

This is the simplest example of a Flask application, perfect for absolute beginners. It demonstrates how to set up a basic web server that returns a simple greeting when accessed.

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

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

Notes

• This application runs on your local machine. When you run it, navigate to http://127.0.0.1:5000/ in your web browser to see the greeting.
• The debug=True parameter helps during development by providing detailed error messages.

Example 2: Simple To-Do List Application

Context

In this example, we’ll create a basic To-Do list application. This example introduces form handling and dynamic content rendering, allowing users to add tasks.

from flask import Flask, render_template, request, redirect

app = Flask(__name__)

tasks = []

@app.route('/')
def home():
    return render_template('index.html', tasks=tasks)

@app.route('/add', methods=['POST'])
def add_task():
    task = request.form.get('task')
    if task:
        tasks.append(task)
    return redirect('/')

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

Notes

• You’ll need an index.html file in a folder named templates. It should contain a form for adding tasks and display the current tasks.
• This example showcases how to use lists and forms in Flask. You can enhance it further by adding features like task deletion or persistence using a database.

Example 3: Basic User Registration Form

Context

This example demonstrates how to create a user registration form. It introduces concepts like form validation and user input handling, which are essential for real-world applications.

from flask import Flask, render_template, request, redirect

app = Flask(__name__)

users = []

@app.route('/register', methods=['GET', 'POST'])
def register():
    if request.method == 'POST':
        username = request.form.get('username')
        password = request.form.get('password')
        if username and password:
            users.append({'username': username, 'password': password})
            return redirect('/success')
    return render_template('register.html')

@app.route('/success')
def success():
    return 'Registration Successful!'

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

Notes

• Create a register.html file in the templates folder to house the registration form.
• This application simulates user registration but does not include secure password handling or database storage. Consider using libraries like Flask-WTF for form handling and validation in more complex apps.

Conclusion

These examples of creating a basic Flask application showcase the framework’s versatility and simplicity. Whether you’re starting with a simple greeting or developing a more complex application like a To-Do list or user registration, Flask provides the tools you need to bring your ideas to life!