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Flask · Module 4 of 10

Forms and validation

Handle forms safely with Flask-WTF.

📖 Key ideas

  1. Flask-WTF integrates WTForms with CSRF protection.
  2. Define a class: class LoginForm(FlaskForm): email = StringField(validators=[DataRequired(), Email()]).
  3. form.validate_on_submit() checks POST and validators.
  4. Set app.config["SECRET_KEY"] for CSRF and sessions.
  5. flash() shows one-time messages.
💡 Real-life example: Flask-WTF is a checklist clipboard that also stamps every form so forgeries are rejected.
Flask-WTFForms extension with CSRF
validate_on_submitChecks submission and validators
SECRET_KEYSigns sessions and tokens
flash()One-time user message