How to use flash() function in flask

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by vsasikalabe dot icon Updated: Oct 11, 2023

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A Flask has a flash() function. It sends a request to the next user. Generally, it is a template. The message parameter is the real message. We should flash this. 

The Next one is the category parameter. It is optional. This will happen as "an error" or "warning". Flask gets messages in a flash by following types,   

  • custom flask messages   
  • python message   
  • flash html flash messages   

The flash() method of the flask module sends the message to the next request. It is an HTML template. Using the flash() method of the flask module, we can generate the messages in the flask script. The flashing system helps record a message at the end of a request. It will access its next request.   

Finally, we can combine the Flash functionality with Bootstrap's JavaScript. This is to make the message visible on the page as well. It helps display only the specified messages. Flask provides the flash() method for client-side scripting languages like JavaScript. It uses the alerts or the Python GUI framework. Tkinter access the dialogue box or the message box. We are using some flashing message command, and we connect this page to login by using the URL /login in the file. It means that when we click on the URL, login redirects us to the login page.   

Advantages of Flask Framework:   

  • It is a lightweight framework that offers hassle-free development.   
  • Provide flexibility to the developer to experiment with their modules or architecture.   
  • It is suitable for small projects.   
  • Offers a built-in development server and a fast debugger.   
  • Easily scalable for the applications.   
  • Support for secure cookies.   

Flasks are a built-in web server, debugger unit testing, and RESTful request dispatching. It also has secure cookies, WSGI compliance, Unicode support, and good documentation. Flask helps make web applications. We can do this by offering tools, libraries, and technologies. It can be a web page, a wiki, a big web-based calendar app, or a commercial website. Flask is a micro-framework. It has no dependencies on external libraries.   

Fig : Preview of the output that you will get on running this code from your IDE.


In this solution, we used the Flask library of Python.


Follow the steps carefully to get the output easily.

  1. Download and Install the PyCharm Community Edition on your computer.
  2. Open the terminal and install the required libraries with the following commands.
  3. Install Flask - pip install flask.
  4. Create a new Python file on your IDE.
  5. Copy the snippet using the 'copy' button and paste it into your python file.
  6. Write if __name__ == '__main__': = True) at the end.
  7. Run the current file to generate the output.

I hope you found this useful. I have added the link to dependent libraries, and version information in the following sections.

I found this code snippet by searching for ' How to display only unique messages when using flash in flask' in Kandi. You can try any such use case!

Environment Tested

I tested this solution in the following versions. Be mindful of changes when working with other versions.

  1. The solution is created in PyCharm 2022.3.
  2. The solution is tested on Python 3.11.1
  3. Flask version- 3.0.0.

Using this solution, we are able to use a flash() function in the flask with simple steps. This process also facilitates an easy-to-use, hassle-free method to create a hands-on working version of code which would help us to use a flash() function in the flask.

Dependent Libraries

flaskby pallets

Python doticonstar image 63300 doticonVersion:2.2.5doticon
License: Permissive (BSD-3-Clause)

The Python micro framework for building web applications.


            flaskby pallets

            Python doticon star image 63300 doticonVersion:2.2.5doticon License: Permissive (BSD-3-Clause)

            The Python micro framework for building web applications.

                      If you do not have the flask library that is required to run this code, you can install it by clicking on the above link.

                      You can search for any dependent library on Kandi like flask.


                      1. What is Flask, and how does it work with other Flask and HTML scripts?   

                      In the Flask, the flash() method helps create informational messages. It creates a message in one view. It renders a function called next in a template view. The flask module's flash() method sends the message to the next request, an HTML template.   


                      2. How can we use client-side scripting with the flask flash function?   

                      Flask creates the flash() method for the client-side scripting language like JavaScript. It uses the alerts or the Python GUI framework. Tkinter uses the dialogue box or the message box.   


                      3. Where do message boxes appear when using Flask Flash for web applications?   

                      Flask provides a function to create information messages for the user. This method is "Flash()". It is a pop-up window or a dialog box on the web page. It sends the message to the next template.   


                      4. Are there any differences between session cookies generated by Flask Flash?   

                      Cookies are small pieces of data that the server sends to the browser. It stores it as key-value pairs. Sessions are a higher-level abstraction. It uses cookies to store a unique identifier for each user. Also, it stores the actual data on the server side.   


                      5. What are some best practices for leveraging Flask in my web applications?   

                      •  Project Structure and Modularity   
                      • Use of Flask Extensions   
                      • App Configuration Management   
                      • Proper Error Handling   
                      • Jinja2 Templating   
                      • Data Validation and Sanitization   
                      • Securing Your Application   
                      • Database Interaction Best Practices


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