Install Flask-WTF in Python Easily

Flask-WTF simplifies form handling in Flask applications. It integrates WTForms with Flask for secure form processing. This guide covers installation and basic usage.

What Is Flask-WTF?

Flask-WTF is a Flask extension for working with web forms. It provides CSRF protection and file upload support. It works seamlessly with WTForms.

The extension helps validate form data easily. It also supports internationalization (i18n). For i18n, you may need Babel.

Prerequisites

Before installing Flask-WTF, ensure you have:

• Python 3.6 or higher
• Flask installed
• Virtual environment (recommended)

If you need user authentication, consider Flask-Login too.

Install Flask-WTF

Use pip to install Flask-WTF. Run this command in your terminal:

pip install Flask-WTF

This installs Flask-WTF and its dependencies. Verify installation with:

pip show Flask-WTF

Basic Flask-WTF Example

Here's a simple form example. Create a file named app.py:

from flask import Flask, render_template
from flask_wtf import FlaskForm
from wtforms import StringField, SubmitField

app = Flask(__name__)
app.config['SECRET_KEY'] = 'your-secret-key'

class MyForm(FlaskForm):
    name = StringField('Name')
    submit = SubmitField('Submit')

@app.route('/', methods=['GET', 'POST'])
def index():
    form = MyForm()
    if form.validate_on_submit():
        name = form.name.data
        return f'Hello, {name}!'
    return render_template('index.html', form=form)

if __name__ == '__main__':
    app.run(debug=True)

The SECRET_KEY is essential for CSRF protection. Never expose it in production.

Create a Template

Make a templates folder. Create index.html inside it:

<form method="POST">
    {{ form.hidden_tag() }}
    {{ form.name.label }} {{ form.name() }}
    {{ form.submit() }}
</form>

This renders the form with CSRF token. The token protects against cross-site request forgery.

Form Validation

Flask-WTF makes validation easy. Add validators to your form fields:

from wtforms.validators import DataRequired

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

The DataRequired validator ensures the field isn't empty. Other validators include Email and Length.

File Uploads

Flask-WTF supports file uploads. Use FileField:

from flask_wtf.file import FileField, FileRequired

class UploadForm(FlaskForm):
    file = FileField('File', validators=[FileRequired()])
    submit = SubmitField('Upload')

Remember to set enctype="multipart/form-data" in your HTML form.

Conclusion

Flask-WTF simplifies form handling in Flask applications. It provides security features like CSRF protection out of the box.

For database migrations in Flask, check Flask-Migrate. For sending emails, see Flask-Mail.

Start using Flask-WTF today to build secure forms in your Flask projects. The integration with WTForms makes it powerful yet simple to use.