Django multiple model update/create

Question

I am a beginning programmer in Django/Python and I am now looking for a way to robustly create and update my models. I would expect this is a very common problem. Some example code of how to do this the right way would be very much appreciated.

Problems which I struggling with is that I am not sure where to put the save() command. Now there are multiple places where I put the save() method. And sometimes I have to multiple times hit the save button on the various views before a change on a low level trickless up to a higher level model.

In this example I use two simplified models named Medium and Circuit. The create methods for the two models are specified as well as a set_medium and set_circuit method, this shows how I am currently doing it.

class Circuit(models.Model):
    medium              = models.ForeignKey('medium.Medium', related_name='medium_related', on_delete=models.CASCADE)
    temperature         = models.FloatField(default=60, help_text='[degC]')
    glycol_percentage   = models.FloatField(default=0, choices = choices.GLYCOL_PERCENTAGE)

    @classmethod
    def create( cls, 
                temperature,
                glycol_percentage):

        circuit = cls(  temperature         = temperature,
                        glycol_percentage   = glycol_percentage)

        circuit.medium = Medium.create(circuit.temperature, circuit.glycol_percentage)
        circuit = circuit.set_circuit(circuit)
        circuit.save()
        return circuit

    def set_circuit(self, circuit):
        circuit.medium.glycol_percentage    = circuit.glycol_percentage
        circuit.medium.temperature          = circuit.temperature
        circuit.medium                      = circuit.medium.set_medium(circuit.medium)
        return circuit

class Medium(models.Model):
    glycol_percentage       = models.FloatField(default=0, choices = choices.GLYCOL_PERCENTAGE)
    temperature             = models.FloatField(default=60, help_text='[degC]')

    # Calculated properties
    rho                     = models.FloatField(default=1000, help_text='[kg/m3]')

    @classmethod
    def create( cls, temperature, glycol_percentage):
        medium = cls(   temperature         = temperature, 
                        glycol_percentage   = glycol_percentage)
        medium = medium.set_medium(medium)
        medium.save()
        return medium

    def set_medium(self, medium):
        medium.rho                     = services.rho(temperature=medium.temperature, glycol_percentage=medium.glycol_percentage)
        return medium

Below is how I typically write my Create and Update views.

class CircuitCreateView(LoginRequiredMixin, CreateView):
    model = Circuit
    template_name = 'circuit/create.html'
    form_class = CircuitForm

    def form_valid(self, form):
        circuit = Circuit.create(   glycol_percentage   = form.cleaned_data['glycol_percentage'],
                                    temperature         = form.cleaned_data['temperature'])
        circuit.save()
        return HttpResponseRedirect(reverse('circuit:detail', args=(circuit.id,)))    

class CircuitUpdateView(LoginRequiredMixin, UpdateView):
    model = Circuit
    template_name = 'circuit/detail-update.html'
    form_class = CircuitForm

    def form_valid(self, form):
        circuit = get_object_or_404(Circuit, pk=self.kwargs['pk_circuit'])
        circuit.glycol_percentage   = form.cleaned_data['glycol_percentage']
        circuit.temperature         = form.cleaned_data['temperature']
        circuit                     = circuit.set_circuit(circuit)
        circuit.save()
        return HttpResponseRedirect(reverse('circuit:detail', args=(circuit.id,)))