Introduction to Flask

Flask is a lightweight WSGI web application framework in Python. It is designed for simplicity and flexibility, allowing developers to build web applications quickly with minimal boilerplate code.

Key features of Flask include:

• Lightweight and modular
• Built-in development server and debugger
• Support for RESTful request dispatching
• Integrated support for unit testing
• Extensive documentation

Flask follows the WSGI (Web Server Gateway Interface) specification, making it compatible with various web servers.

To install Flask, ensure you have Python installed on your system. You can install Flask using pip:

pip install Flask

To verify the installation, run the following command:

python -m flask --version

A basic Flask application consists of a single Python file. Below is a simple example:

from flask import Flask

app = Flask(__name__)

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

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

This code creates a basic web server that responds with "Hello, World!" when accessed at the root URL.

Routing in Flask allows you to bind URLs to functions. You can create multiple routes for different web pages:

@app.route('/about')
def about():
    return 'About Page'

This example shows how to create an "About" page that responds to the `/about` URL.

Flask supports Jinja2 templating, allowing you to separate HTML from Python code. Here's an example:

from flask import render_template

@app.route('/hello/')
def hello(name):
    return render_template('hello.html', name=name)

In the `hello.html` template, you can display the `name` variable passed from the route:

<h1>Hello, {{ name }}!</h1>