Nanny-Level Tutorial: Flask Form Validation and Data Processing

This article introduces the methods of using `Flask-WTF` for form validation and data processing in Flask. Form validation in web applications ensures data legitimacy and security, preventing invalid/malicious data. `Flask-WTF` is implemented based on `WTForms` and requires installing `flask-wtf` and optionally `flask-sqlalchemy`. Key steps: 1. Initialize the Flask application and configure `SECRET_KEY` (for CSRF protection), define form classes, and add validators (e.g., `DataRequired`, `Email`) to fields for required checks, length restrictions, and format verifications. 2. In view functions, distinguish between GET/POST requests, validate data via `form.validate_on_submit()`, process data (e.g., database storage) after successful validation, and display errors if validation fails. 3. Support custom validators (e.g., password complexity checks); define models (e.g., `User` class) for data storage, and use password hashing (e.g., bcrypt) in production environments. Notes: Templates must include `{{ form.hidden_tag() }}` to generate CSRF tokens, `SECRET_KEY` should be securely stored, and custom validators must raise `ValidationError`. Through these steps, robust form processing can be achieved.