How To Use Flask-WTForms

Make form validation a breeze

Photo by Alejandro Escamilla on Unsplash

Meta Information

Goals

• Introduction on how to use Flask-WTForms to simplify form generation and validation
• Use Flask-WTForms to build a functioning Flask application with only one registration page. The end product looks like:

A registration form with a customized style

Assumption of readers

• Know Python.
• Know the basics of Flask.

Code

• The code for this article can be accessed on GitHub.

What Is Flask-WTForms

When you are building an interactive application using Flask, you can’t avoid forms. Code for creating forms and processing form data, especially form validation, can quickly grow to something that is difficult to read as well as tedious to write.

Flask-WTForms is a great tool to help with form validation (e.g., avoidance of Cross-Site Request Forgery (CSRF)). Flask-WTForms can help create and use web forms with simple Python models, turning tedious and boring form validation into a breeze.

Use Flask-WTForms

The codebase of a simple Flask application

To demonstrate the power of Flask-WTForms, we will keep our codebase to a minimum. As a result, we will stick to a single Python file and an HTML template.

To start from scratch, we create a folder named wtf-registration-form, navigate inside the folder, create and activate the virtual environment, and then install Flask:

$ python3.7 -m venv env
$ source env/bin/activate
(env)$ pip install flask

Our codebase app.py has only about 10 lines: