flask-login: can't understand how it works

Question

I\'m trying to understand how Flask-Login works.

I see in their documentation that they use a pre-populated list of users. I want to play with a database-stored user

Answer 1

Flask-login will try and load a user BEFORE every request. So yes, your example code below will be called before every request. It is used to check what userid is in the current session and will load the user object for that id.

@login_manager.user_loader
def load_user(userid):
    #print 'this is executed',userid
    return user(userid, 'asdf')        

If you look at the Flask-login source code on github, there is a line under function init_app which goes:

app.before_request(self._load_user)

So before every request, the _load_user function is called. The _load_user functions actually calls another function "reload_user()" based on conditions. And finally, reload_user() function calls your callback function that you wrote (load_user() in your example).

Also, flask-login only provides the mechanism to login/logout a user. It does not care if you are using mysql database.