Introduction

There are various ways in which we can design and implement forms in a web application. With the advent of Web 2.0, form validation and communicating correct messages to the user has become very important. Client-side validations can be implemented at the frontend using JavaScript and HTML5. Server-side validations have a more important role in adding security to the application rather than being interactive. Server-side validations prevent any incorrect data from going through to the database and, hence, curb frauds and attacks.

WTForms provides a lot of fields with server-side validation by default and, hence, increases the development speed and decreases the overall effort. It also provides the flexibility to write custom validations and custom fields as needed.

We will use a Flask extension for this chapter. This extension is called Flask-WTF (https://flask-wtf.readthedocs.org/en/latest/); it provides a small integration between WTForms and Flask and takes care of important...