How Flask Works Python

Python Programming

As a developer who has had the pleasure of working with Flask, I can confidently say that it is a powerful and flexible web framework for building web applications using Python. In this article, I will take you on a deep dive into how Flask works and share my personal insights and commentary along the way.


Flask is a micro web framework written in Python. It is designed to be a simple and lightweight tool for creating web applications with minimal dependencies and a small learning curve. Flask follows the WSGI (Web Server Gateway Interface) standard, which allows it to seamlessly integrate with various web servers.

One of the key features of Flask is its use of routes and views. Routes define the URLs that your application will respond to, while views are the functions that handle these requests and generate responses. Let’s take a closer look at how Flask handles routing and view functions.

Routing and View Functions

When a request is made to a Flask application, Flask uses the route information to determine which view function should handle the request. This process is known as routing. Routes in Flask are defined using decorators, which are special Python syntax that modify the behavior of a function.

For example, consider the following Flask route:


This route decorator tells Flask that the following function should handle requests to the ‘/hello’ URL. The function itself is known as a view function. Here’s an example of a simple Hello World view function:

def hello():
return 'Hello, World!'

When a user opens the ‘/hello’ URL in their browser, Flask will call the ‘hello’ function and return the string ‘Hello, World!’ as the response. You can also return HTML templates, JSON data, or any other type of response from a view function.

Flask also allows you to pass variables to view functions using dynamic routes. For example, consider the following route:


This route matches any URL that starts with ‘/user/’ followed by a username. The username value is then passed as an argument to the corresponding view function:

def show_user_profile(username):
return f'User: {username}'

By accessing the ‘/user/johndoe’ URL, Flask will call the ‘show_user_profile’ function with the username argument set to ‘johndoe’, and return the string ‘User: johndoe’ as the response.

Templates and Static Files

Flask also offers a powerful templating engine called Jinja2, which allows you to separate your HTML code from your Python code. With Jinja2, you can create reusable templates and easily pass data from your view functions to your templates.

Static files, such as CSS stylesheets, JavaScript files, and images, can also be served by Flask. By placing these files in a designated ‘static’ directory, Flask automatically handles their serving. You can simply link to these static files in your HTML templates using the appropriate paths.


Flask is a versatile and user-friendly web framework that allows developers to quickly build powerful web applications with ease. Its simplicity, flexibility, and extensive documentation make it a popular choice among Python developers.

In this article, we explored how Flask handles routing and view functions, as well as its support for templates and static files. By harnessing the power of Flask, developers can create robust and dynamic web applications that are a joy to work with.