Forms & Validation with Flask-WTF

🐍 FlaskLesson 12Intermediate

Flask-WTF integrates Flask with WTForms, providing secure form rendering, validation logic, and built-in CSRF protection mechanisms.

1 Secure WTForms Class

Python — forms.py

from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, SubmitField
from wtforms.validators import DataRequired, Email, Length

class RegistrationForm(FlaskForm):
    username = StringField("Username", validators=[DataRequired(), Length(min=4, max=25)])
    email = StringField("Email", validators=[DataRequired(), Email()])
    password = PasswordField("Password", validators=[DataRequired(), Length(min=8)])
    submit = SubmitField("Register")

2 Code Challenge

Challenge: Write a template showing registration fields. Ensure the template renders error messages dynamically next to input fields when form validation fails.