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ReCaptcha in Django Forms

Using ReCaptcha widgets in forms managed by Django

ReCaptcha is a popular system for bot-blocking forms. The API allows integration of the ReCaptcha widget on our sites. In case of Python we can use recaptcha-client, which is used by a Django sippet adding form field for Django forms. In this article I'll show you simple example based on that snippet

Code for widgets.py:
from django import forms
from django.utils.safestring import mark_safe
from django.conf import settings
from recaptcha.client 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)] 
Code for 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 recaptchawidget.widgets import ReCaptcha
from recaptcha.client 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] 

Now you can use ReCaptcha widgets in your forms. Here is an example form definition:
from django import forms

from recaptchawidget.fields import ReCaptchaField 

class RegisterProForm(forms.Form):
    A form with recaptcha
    login = forms.CharField(min_length=2, max_length=30)
    recaptcha = ReCaptchaField()
And a view that manages the form:
# -*- coding: utf-8 -*-

from django.shortcuts import render_to_response
from django.http import HttpResponseRedirect
from django.template import RequestContext

from myform.forms import *

def show_form(request):
    Recaptcha example
    form = RegisterProForm()
    if request.POST:
        form = RegisterProForm(request.POST)
        if form.is_valid():
            print 'ok'
            return HttpResponseRedirect('/')
    return render_to_response('myform.html', {'form': form}, context_instance=RequestContext(request))
And the template:
<form action="./" method="post">{% csrf_token %}
    {{ form.login }}{% if form.login.errors %}<div class="errmsg">{{ form.login.errors|join:", " }}</div>{% endif %}<br />
    {{ form.recaptcha }}{% if form.recaptcha.errors %}<div class="errmsg">{{ form.recaptcha.errors|join:", " }}</div>{% endif %}<br />
    <input type="submit" value="Send Form" />
We are all done. The ReCaptcha widget will be validated as any other Django form field.

Django web framework tutorials, 1 February 2011,

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