Flask Framework Cookbook - Second Edition

Validating fields on the server side

We have forms and fields, but we need to validate them in order to make sure that only the correct data goes through to the database, and that errors are handled beforehand, rather than corrupting the database. These validations can also prevent the application against cross-site scripting (XSS) and CSRF attacks. WTForms provides a whole lot of field types that themselves have validations written for them by default. Apart from these, there are a bunch of validators that can be used on the basis of choice and need. In this recipe, we will use a few of them to understand the concept.