Too much logic in a post method? You're probably right.

views.py

      def post(self, request, *args, **kwargs):
        form = CheckoutForm(request.POST)
        if form.is_valid():
            user = request.user
            stripe.api_key = settings.STRIPE_SECRET
            token = form.cleaned_data['stripe_token']
            quantity = form.cleaned_data.get('quantity', 1)
            customer = stripe.Customer.retrieve(user.stripe_customer_id)
            customer.card = token
            customer.save()

            if user.stripe_subscription_id is None:
                subscription = customer.subscriptions.create(plan=form.cleaned_data['sub_type'], quantity=quantity)
                user.stripe_subscription_id = subscription.id
                user.save()
            else:
                subscription = customer.subscriptions.retrieve(user.stripe_subscription_id)

                original_plan = subscription.plan
                selected_plan = form.cleaned_data['sub_type']

                if original_plan == selected_plan:
                    original_quantity = subscription.quantity
                    subscription.quantity = original_quantity + quantity
                    subscription.save()
                else:
                    subscription.delete()
                    newsub = customer.subscriptions.create(plan=selected_plan, quantity=quantity)
                    user.stripe_subscription_id = newsub.id
                    user.save()

            # Update User Data
            user.first_name = form.cleaned_data['first_name']
            user.last_name = form.cleaned_data['last_name']
            user.company_name = form.cleaned_data.get('company_name', '')
            user.address = form.cleaned_data['address']
            user.city = form.cleaned_data['city']
            user.state = form.cleaned_data['state']
            user.zip = form.cleaned_data['zipcode']
            user.country = form.cleaned_data['country']
            user.cc_type = form.cleaned_data['cc_type']
            user.last_4 = form.cleaned_data['last_4']
            user.save()

            return redirect('account:index')

        return render(request, self.template, {'form': form, 'stripe_key': settings.STRIPE_PUBLISHABLE})