Marco Fucci

How to integrate reCAPTCHA with Django using a field and a widget.

From reCAPTCHA:

reCAPTCHA is a free CAPTCHA service that helps to digitize books, newspapers and old time radio shows.
A CAPTCHA is a program that can tell whether its user is a human or a computer.

You'll probably see one if you want to sign up for google apps, twitter, last.fm etc.

Although you can find a good solution on djangosnippets, I'll show you how to add reCAPTCHA in your form without writing the same code again and again.

Step 1: Apply for a reCAPTCHA key

Register on reCAPTCHA to get your public/private key pair.

Step 2: Add your keys in settings.py

RECAPTCHA_PUBLIC_KEY = '<your public key>'
RECAPTCHA_PRIVATE_KEY = '<your private key>'

Step 3: Add recaptcha-client to your project

Download recaptcha-client, create a folder (recaptcha) in your project with a copy of captcha.py inside.

Step 4: Put ReCaptchaField and ReCaptcha widget somewhere

I prefer to use a generic app (marcofucci_utils) with 2 files:

fields.py

from django.conf import settings
from django import forms
from django.utils.encoding import smart_unicode
from django.utils.translation import ugettext_lazy as _

from marcofucci_utils.widgets import ReCaptcha
from recaptcha import captcha

class ReCaptchaField(forms.CharField):
    default_error_messages = {
        'captcha_invalid': _(u'Invalid captcha')
    }

    def __init__(self, *args, **kwargs):
        self.widget = ReCaptcha
        self.required = True
        super(ReCaptchaField, self).__init__(*args, **kwargs)

    def clean(self, values):
        super(ReCaptchaField, self).clean(values[1])
        recaptcha_challenge_value = smart_unicode(values[0])
        recaptcha_response_value = smart_unicode(values[1])
        check_captcha = captcha.submit(recaptcha_challenge_value, 
            recaptcha_response_value, settings.RECAPTCHA_PRIVATE_KEY, {})
        if not check_captcha.is_valid:
            raise forms.util.ValidationError(self.error_messages['captcha_invalid'])
        return values[0]

and widgets.py

from django import forms
from django.utils.safestring import mark_safe
from django.conf import settings
from recaptcha import captcha

class ReCaptcha(forms.widgets.Widget):
    recaptcha_challenge_name = 'recaptcha_challenge_field'
    recaptcha_response_name = 'recaptcha_response_field'

    def render(self, name, value, attrs=None):
        return mark_safe(u'%s' % captcha.displayhtml(settings.RECAPTCHA_PUBLIC_KEY))

    def value_from_datadict(self, data, files, name):
        return [data.get(self.recaptcha_challenge_name, None), 
            data.get(self.recaptcha_response_name, None)]

Step 5: Configure your app

I'll use django-registration because I'm lazy, but you can write your own form in the same way.

Follow these steps:

• Download django-registration
• Add registration to the INSTALLED_APPS setting of your Django project
• Create a custom app registration_app with urls.py and forms.py inside

• Add this line to <your-project>.urls.py
  

  (r'^accounts/', include('registration_app.urls')),

registration_app.forms

from django import forms

from marcofucci_utils import fields as marcofucci_fields

from registration.forms import RegistrationForm

class RecaptchaRegistrationForm(RegistrationForm):
    recaptcha = marcofucci_fields.ReCaptchaField()

registration_app.urls

from django.conf.urls.defaults import *
from registration.views import register

from registration_app.forms import RecaptchaRegistrationForm

urlpatterns = patterns('',
    url(r'^register/$', register,
        {'form_class': RecaptchaRegistrationForm},
        name='registration.views.register'),
    (r'', include('registration.urls')),
)

registration_app is now a 100% drop-in replacement for django-registration (Thanks to Ian for this).

That's it!

Note that we have used just 1 custom line of code (recaptcha = marcofucci_fields.ReCaptchaField()).

Let's take a look at http://localhost:8000/accounts/register/

In conclusion

You can either write your custom code again and again making mistakes and wasting time or write your code once and have fun!