Building a Simple Web Application with Flask

Flask is a lightweight and easy-to-use web framework for Python. In this article, we'll walk through the basics of creating a simple web application using Flask. Whether you're a beginner in web development or looking to prototype a project quickly, Flask provides a great starting point.

Installing Flask

Before we start, make sure you have Python installed on your machine. You can install Flask using the following command:

pip install flask

Creating a Simple Flask App

Let's create a minimal Flask application. Create a file named app.py with the following content:

from flask import Flask
  
app = Flask(__name__)
                      
@app.route('/')
def home():
    return 'Hello, Flask!'

This code defines a basic Flask app with a single route '/' that returns the string 'Hello, Flask!' when you visit the home page.

Running the Flask App

To run your Flask app, execute the following commands in your terminal or command prompt:

export FLASK_APP=app.py  # For Linux/macOS
set FLASK_APP=app.py  # For Windows
                      
flask run

Visit http://127.0.0.1:5000/ in your web browser, and you should see the 'Hello, Flask!' message.

Adding Dynamic Routes

Flask allows you to create dynamic routes by adding variable parts to the URL. Let's modify our app to greet the user with a custom message:

from flask import Flask, render_template
  
app = Flask(__name__)
                      
@app.route('/')
def home():
    return 'Hello, Flask!'
                      
@app.route('/greet/<name>')
def greet(name):
    return f'Hello, {name}!'

Now, visiting http://127.0.0.1:5000/greet/John will display 'Hello, John!'

Using Templates for HTML

Flask allows you to render HTML templates for a more sophisticated web application. Create a folder named templates in the same directory as your app.py and add a file named index.html with the following content:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Flask App</title>
</head>
<body>
    <h1>{{ message }}</h1>
</body>
</html>

Modify your Flask app to render this template:

from flask import Flask, render_template
  
app = Flask(__name__)
                      
@app.route('/')
def home():
    return render_template('index.html', message='Hello, Flask!')

This code renders the index.html template with a custom message.

Conclusion

Congratulations! You've built a simple web application with Flask. This is just the beginning—Flask offers much more for creating robust and feature-rich web applications. As you continue your journey in web development, explore Flask's documentation and build upon this foundation to create more complex projects.

Stay tuned for future articles where we'll explore advanced Flask features and real-world web application development.

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