How can I validate forms in Django using WTForms?

How can I validate forms in Django using WTForms?

You can validate forms in Django using WTForms by creating a form class that inherits from FlaskForm and defining your fields with validation rules.

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, PasswordField, SubmitField
from wtforms.validators import DataRequired, Length

class LoginForm(FlaskForm):
    username = StringField('Username', validators=[DataRequired(), Length(min=4, max=25)])
    password = PasswordField('Password', validators=[DataRequired(), Length(min=6, max=35)])
    submit = SubmitField('Login')

What if I want to add custom validation?

You can add custom validation by defining a method in your form class and using the @validates decorator. For example:

from wtforms import ValidationError

class LoginForm(FlaskForm):
    # ... your fields here

    def validate_username(self, username):
        if username.data == 'admin':
            raise ValidationError('Username cannot be admin.')

How do I display validation errors in my template?

You can display validation errors in your template by checking for errors in the form object. For example:

<form method="POST">
    {{ form.hidden_tag() }}
    {{ form.username.label }}
    {{ form.username(size=32) }}
    {% for error in form.username.errors %}
        <span style="color: red;">{{ error }}</span>
    {% endfor %}
    {{ form.submit() }}
</form>