How can I handle errors in Flask-WTF forms?

How can I handle errors in Flask-WTF forms?

You can handle errors in Flask-WTF forms by using the validate_on_submit() method and checking for form errors.

Can you show me an example of how to implement that?

Sure! Here's a simple example:

from flask import Flask, render_template, redirect, url_for, flash
from flask_wtf import FlaskForm
from wtforms import StringField, SubmitField
from wtforms.validators import DataRequired

app = Flask(__name__)
app.secret_key = 'your_secret_key'

class MyForm(FlaskForm):
    name = StringField('Name', validators=[DataRequired()])
    submit = SubmitField('Submit')

@app.route('/', methods=['GET', 'POST'])
def index():
    form = MyForm()
    if form.validate_on_submit():
        flash('Form submitted successfully!')
        return redirect(url_for('index'))
    return render_template('index.html', form=form)

This will show validation errors if the form is not filled out correctly.

What if I want to display the error messages on the same page?

You can display error messages in your template by checking form.errors. For example:

{% for field, errors in form.errors.items() %}
    {% for error in errors %}
        <div class="error">{{ field.label }}: {{ error }}</div>
    {% endfor %}
{% endfor %}