Flask-WTF offers simple integration with WTForms. This integration includes optional CSRF handling for greater security.
Source code and issue tracking at Bitbucket.
Install with pip and easy_install:
pip install Flask-WTF
or download the latest version from Bitbucket:
hg clone http://bitbucket.org/danjac/flask-wtf
cd flask-wtf
python setup.py develop
If you are using virtualenv, it is assumed that you are installing Flask-WTF in the same virtualenv as your Flask application(s).
The following settings are used with Flask-WTF:
- CSRF_ENABLED default True
- CSRF_SESSION_KEY default _csrf_token
CSRF_ENABLED enables CSRF. You can disable by passing in the csrf_enabled parameter to your form:
form = MyForm(csrf_enabled=False)
Generally speaking it’s a good idea to enable CSRF. There are two situations where you might not want to: unit tests and AJAX forms. In the first case, switching CSRF_ENABLED to False means that your forms will still work (and the CSRF hidden field will still be printed) but no validation will be done. In the second, CSRF validation is skipped if request.is_xhr is True (you can’t do cross-domain AJAX anyway, so CSRF validation is redundant).
The CSRF_SESSION_KEY sets the key used in the Flask session for storing the generated token string. Usually the default should suffice, in certain cases you might want a custom key (for example, having several forms in a single page).
Both these settings can be overriden in the Form constructor by passing in csrf_enabled and csrf_session_key optional arguments respectively.
In addition, there are additional configuration settings required for Recaptcha integration : see below.
Flask-WTF provides you with all the API features of WTForms. For example:
from flaskext.wtf import Form, TextField, Required
class MyForm(Form):
name = TextField(name, validators=[Required()])
In addition, a CSRF token hidden field is created. You can print this in your template as any other field:
<form method="POST" action=".">
{{ form.csrf }}
{{ form.name.label }} {{ form.name(size=20) }}
<input type="submit" value="Go">
</form>
However, in order to create valid XHTML/HTML the Form class has a method hidden_tag which renders any hidden fields, including the CSRF field, inside a hidden DIV tag:
<form method="POST" action=".">
{{ form.hidden_tag() }}
The safe filter used to be required with WTForms in Jinja2 templates, otherwise your markup would be escaped. For example:
{{ form.name|safe }}
However widgets in the latest version of WTForms return a HTML safe string so you shouldn’t need to use safe.
Ensure you are running the latest stable version of WTForms so that you don’t need to use this filter everywhere.
The Form instance automatically appends a file attribute to any FileField field instances if the form is posted.
This file attribute is an instance of Werkzeug FileStorage instance from request.files.
For example:
from werkzeug import secure_filename
class PhotoForm(Form):
photo = FileField("Your photo")
@app.route("/upload/", methods=("GET", "POST"))
def upload():
form = PhotoForm()
if form.validate_on_submit():
filename = secure_filename(form.photo.file.filename)
else:
filename = None
return render_template("upload.html",
form=form,
filename=filename)
Remember to set the enctype of your HTML form to multipart/form-data to enable file uploads:
<form action="." method="POST" enctype="multipart/form-data">
....
</form>
Flask-WTF also provides Recaptcha support through a RecaptchaField:
from flaskext.wtf import Form, TextField, RecaptchaField
class SignupForm(Form):
username = TextField("Username")
recaptcha = RecaptchaField()
This field handles all the nitty-gritty details of Recaptcha validation and output. The following settings are required in order to use Recaptcha:
- RECAPTCHA_USE_SSL : default False
- RECAPTCHA_PUBLIC_KEY
- RECAPTCHA_PRIVATE_KEY
- RECAPTCHA_OPTIONS
RECAPTCHA_OPTIONS is an optional dict of configuration options. The public and private keys are required in order to authenticate your request with Recaptcha - see documentation for details on how to obtain your keys.
If flaskext-babel is installed then Recaptcha message strings can be localized.
The Form class provided by Flask-WTF is the same as for WTForms, but with a couple of changes. Aside from CSRF validation, a convenience method validate_on_submit is added:
from flask import Flask, request, flash, redirect, url_for, \
render_template
from flaskext.wtf import Form, TextField
app = Flask(__name__)
class MyForm(Form):
name = TextField("Name")
@app.route("/submit/", methods=("GET", "POST"))
def submit():
form = MyForm()
if form.validate_on_submit():
flash("Success")
return redirect(url_for("index"))
return render_template("index.html", form=form)
Note the difference from a pure WTForms solution:
from flask import Flask, request, flash, redirect, url_for, \
render_template
from flaskext.wtf import Form, TextField
app = Flask(__name__)
class MyForm(Form):
name = TextField("Name")
@app.route("/submit/", methods=("GET", "POST"))
def submit():
form = MyForm(request.form)
if request.method == "POST" and form.validate():
flash("Success")
return redirect(url_for("index"))
return render_template("index.html", form=form)
validate_on_submit will automatically check if the request method is PUT or POST.
You don’t need to pass request.form into your form instance, as the Form automatically populates from request.form unless specified. Other arguments are as with wtforms.Form.