Flask user authentication

I don't think that flask has any authentication built-in, only support for tracking sessions.

Here are some snippets for basic HTTP authentication and authentication with some third-party providers. Otherwise you will need to roll your own or use a framework that has this baked in (like Django)

Here is a discussion thread on this topic with a useful link

I would suggest using the flask-login extension, it makes session management really easy to add to your flask application, and provides a nice documentation which covers in details every aspect of the extension.