#settings.py

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


#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)]


#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]


#forms.py

    class RegistrationForm(forms.Form):
        ...
        recaptcha = marcofucci_fields.ReCaptchaField()
        ...