Django's Class base view, checking params and dispatch to either valid or invalid case method.

params.py

from django.http import HttpResponseRedirect
from django.views.generic.base import TemplateResponseMixin, View

class ParamMixin(object):
    failed_url = None
    allowed_params = None

    def get_failed_url(self):
        return self.failed_url

    def is_param_valid(self, **kwargs):
        for k in kwargs.keys():
            if k not in self.allowed_params:
                return False

        return True

    def param_valid(self, **kwargs):
        context = self.get_context_data(**kwargs)
        return self.render_to_response(context)

    def param_invalid(self):
        return HttpResponseRedirect(self.get_failed_url())

    def get_context_data(self, **kwargs):
        return kwargs


class ProcessParamView(View):
    def get(self, request, *args, **kwargs):
        kwargs = request.GET
        self.failed_url = request.path

        if self.is_param_valid(**kwargs):
            return self.param_valid(**kwargs)
        else:
            return self.param_invalid()


class ParamView(ParamMixin, TemplateResponseMixin, ProcessParamView):
    """
    """


class MyParamView(ParamView):
    template_name = 'myparams.html'
    allowed_params = ('spam', 'ham')