Both parameters are optional. Let us now see a simple example, demonstrating the flashing mechanism in Flask. message parameter is the actual message to be flashed. I'm going to need a simple web form that accepts the message: app/main/forms.py: Private message form class. Like I was saying before, we actually do not need to do anything but call the flash function when we wish to flash a message, and we do not need to pass it to the HTML, since it is built into flask, and it will be passed on its own. Then when login is successful, we should the message in the template with the get_flashed_messages function. We create the flash message with the flash function in app.py. flask documentation: Message Flashing. return render_template("home.html") The surprising thing to many is that calling flash () doesn't make your message show up on your template. Flask flash messages as Bootstrap alert. These messages need to be extracted in the template from the session. This page shows Python examples of flask.flash. In case of error, the login template is redisplayed with error message. In the routes.py file, we can see how the two messages are pushed to the template context. category: the message's category, the default is message. This is usually combined with a … In order to remove message from session, template calls get_flashed_messages(). For implementing message flashing, Flask module contains a flash () function, which passes on the message to the next request, which is generally a template. The Flask flash method shows messages to the users. It just adds the message to the message store. A good GUI based application provides feedback to a user about the interaction. This is ideal for cases when we want to provide the user with some feedback based on the actions of their current request, take this scenario for example: In the following code, a ‘/’ URL displays link to the login page, with no message to flash. And now I was stuck in a point.The problem is that I need to display the balance quantity of an item to the text box or as a message in to the html page when the user entered quantity, greater than the balance quantity in that location. @app.route(' /flash ') def just_flash(): flash(' I am flash, who is looking for me? ') {% with messages = get_flashed_messages(with_categories=true) %}