How Flask works

Understanding Flask

Flask is a micro web framework written in Python. It does not require any particular tools or libraries, which makes it simple and easy to use. It has a modular design, which means it can be easily extended with various extensions available. This makes Flask a very flexible and adaptable tool, suitable for both small and large projects.

How Flask Works

At the heart of Flask is the WSGI (Web Server Gateway Interface). This is a standard interface between web servers and web applications. When you run a Flask application, you're running a WSGI application.

When a client (like a web browser) sends a request to your server, it first hits the WSGI server, which passes the request to your Flask application. Your Flask application then processes the request and sends a response back to the WSGI server, which then sends it back to the client. This is the basic flow of a Flask application.

The Application and Request Context

Flask uses a concept of contexts to temporarily make certain objects globally accessible. There are two types of contexts in Flask: the application context and the request context.

The application context keeps track of the application-level data throughout a request, while the request context contains all the request-specific data.

These contexts are automatically managed by Flask. When a request is received, Flask pushes the application and request contexts. When the request is done, Flask pops these contexts.

Routing in Flask

Routing is the process of associating a URL with a Python function. In Flask, you use the @app.route() decorator to define routes. The function associated with a route is called a view function, and it returns the response that gets sent back to the client.

Here's an example of a simple route:

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

When you visit the root URL (/), the home function is called and 'Hello, World!' is returned as the response.

Templates in Flask

Flask uses a template engine called Jinja2 to generate dynamic HTML content. You define templates in separate HTML files, and then you can render these templates in your view functions using the render_template() function.

Here's an example of how to render a template:

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

In this example, Flask will look for a template called home.html in the templates folder, and it will use this template to generate the HTML response.

Conclusion

This has been a high-level overview of how Flask works. Flask is a powerful and flexible tool that is easy to learn and use. Its modular design and extensive use of decorators make it a joy to work with. As you continue to learn more about Flask, you'll discover all the ways you can use it to build dynamic and robust web applications.