Dynamic forms with class based generic views.

forms.py

class SearchForm(forms.Form):
    """
    Search for users.
    """
    # Search fields.
    first_name = forms.CharField()
    last_name = forms.CharField()
    email = forms.CharField()


class SearchResultsForm(forms.Form):
    """
    Display a list of matching users as (in this case) radio buttons.
    """
    users = forms.ChoiceField(label='Search results', choices=(),
                              widget=forms.RadioSelect())

    def __init__(self, search_terms, *args, **kwargs):
        super(SearchResultsForm, self).__init__(*args, **kwargs)
        # Get the matching users and add them as choices to a radio button input.
        choices = api.fetch_users(first_name=first_name, last_name=last_name,
                                 email=email)
        self.fields['users'].choices = choices

views.py

class SearchView(FormView):
    template_name = 'search.html'
    form_class = SearchForm

    def get_success_url(self):
        return reverse('search_results')

    def form_valid(self, form):
        # Add the inputs from the form to the session data.
        self.request.session['search_terms'] = {
            'first_name': form.cleaned_data.get('first_name'),
            'last_name': form.cleaned_data.get('last_name'),
            'email': form.cleaned_data.get('email'),
        }
        return HttpResponseRedirect(self.get_success_url())

class SearchResultsView(FormView):
    template_name = 'search_results.html'
    form_class = SearchResultsForm

    def get_success_url(self):
        reverse('search_complete')

    def get_form(self, form_class):
        search_terms = self.request.session.get('search_terms')
        return form_class(search_terms=search_terms,
                          **self.get_form_kwargs())