http://chriskief.com/2012/12/22/django-register-with-oauth-google/

google.py

import urllib
from django.conf import settings
from django.core.urlresolvers import reverse
from django.core.context_processors import csrf


def get_authorization_url(request):

        # URL to where we will redirect to
        redirect_url = urllib.quote_plus(settings.SITE_URL + reverse('register_google'))

        # create a unique state value for CSRF validation
        request.session['google_state'] = unicode(csrf(request)['csrf_token'])

        scope = urllib.quote_plus('https://www.googleapis.com/auth/userinfo.email') + '+' + \
                urllib.quote_plus('https://www.googleapis.com/auth/userinfo.profile')

        # redirect to google for approval
        url = 'https://accounts.google.com/o/oauth2/auth?' \
              + 'scope=' + scope \
              + '&state=' + request.session['google_state'] \
              + '&redirect_uri=' + redirect_url \
              + '&response_type=code' \
              + '&client_id=' + settings.GOOGLE_OAUTH2_CLIENT_ID \
              + '&access_type=offline' \
              + '&approval_prompt=auto'

        return url