Flask User Authentication: Implementing Login Functionality with Flask-Login

This article introduces the method to implement user login functionality in web applications using Flask-Login. As a lightweight extension, Flask-Login simplifies user session management, login/logout operations, and permission control. The core steps include: installing `flask` and `flask-login`; initializing the application and configuring `LoginManager` with a redirect route for unauthenticated access; creating a user model that inherits from `UserMixin` to define user ID, password, and other information; loading the user from the session via the `user_loader` callback function; implementing login view to validate credentials and using `login_user` to record the session, while `logout_user` is used for logout; and protecting routes requiring authentication with the `@login_required` decorator. A mock user database and template rendering are used to support the basic login flow. Notices emphasize secure password storage (hashing), secure session key configuration, and suggest extending with features like "remember me" and permission management. Flask-Login enables quick implementation of core authentication functionality through a concise API, making it suitable for rapid entry into web user authentication development.