A Flask request from start to finish

by David Lord

flask wsgi internals

Even though Flask is a 'micro' framework, it's doing quite a lot between receiving a request and returning a response. Learn about the lifecycle of a Flask request and how you can get in the middle of it to make your app more powerful.

Your first experience with Flask was probably writing a function that returned a string. Flask got a request from your browser, called the function, and returned the string as a response. Even when you build more complex applications, you may not get more complicated than that. But Flask contains a rich internal API for controlling how a request moves through the application and becomes a response, and it's possible to override or extend every part.

This talk will explore the path a request takes through, from being received from the WSGI server to building a response. See how routing, the request context, event handlers, signals, error handlers, the response formatter, extensions, and middleware all play a part behind the scenes in turning your Python function into a web application. Some common entry points for customization will be demonstrated, but the focus is on the overall execution path.

Flask (and Django, etc.) may seem magical, but they all follow a fundamental set of steps and rules. Demystify Flask and take control of your application."

About the Author

I’m a core maintainer of Flask and the other Pallets projects (Werkzeug, Jinja, Click, ItsDangerous, MarkupSafe), as well as numerous smaller libraries. I manage the Pallets open source organization, review patches, write documentation, make releases, and occasionally write some code myself. :-) I’ve been working with Python for 10 years, and Flask et. al. for 6, and I’m still learning new things that I want to share with others.

Author website: https://davidism.com/