http://chriskief.com/2013/05/17/django-mixins-requiresigninajax-and-jsonresponsemixin/

jsonresponse.py

import json
from django.http import HttpResponse


class JSONResponseMixin(object):

    # a mixin that can be used to render a JSON response
    response_class = HttpResponse

    def render_to_response(self, context, **response_kwargs):
        # returns a JSON response, transforming 'context' to make the payload
        response_kwargs['content_type'] = 'application/json'
        return self.response_class(self.convert_context_to_json(context), **response_kwargs)

    def convert_context_to_json(self, context):
        # this would need to be a bit more complex if we're dealing with more complicated variables
        return json.dumps(context)