Implementing flash messages in Flask

Flash messages enhance the user experience in any web application, providing informative and timely feedback to users. Flash is used to display status or error messages on web pages after a redirect. For instance, after a successful form submission, a message can be stored in the flash to display a success message on the redirected page.

The flash message is stored in the user’s session, which is a dictionary-like object that can store information between requests. With flash messages, you can pass information between requests securely and efficiently. This is useful for displaying messages that don’t need to persist for a long time or that need to be shown only once, such as success or error messages. Since flash messages are stored in the user’s session, they are only accessible by the server and are not sent to the client in plain text, making them secure.

Let’s modify the login and logout endpoints to show flash...