How do I validate WTForms in Flask?

How do I validate WTForms in Flask?

To validate WTForms in Flask, you can use the built-in validators provided by WTForms. You need to define your form class and specify the validation rules for each field.

Can you give me an example of a form with validation?

Sure! Here's a simple example:

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

class MyForm(FlaskForm):
    name = StringField('Name', validators=[DataRequired(), Length(min=2, max=30)])
    submit = SubmitField('Submit')

What happens if the validation fails?

If validation fails, the form will not be submitted, and you can display error messages to the user. You can access the errors using form.errors.

How can I display these error messages in my template?

You can loop through the form errors in your template like this:

{% for field in form %}
    {% for error in field.errors %}
        <div class="error">{{ error }}</div>
    {% endfor %}
{% endfor %}