Update field on another table when submitting form – django

I have a form where adding appointments. I would like to update a field in another table during submission. Let me illustrate:

accounts model (Custom user model)

class Account(AbstractBaseUser):

    patient_status = (     
        ('No Patient', _('No Patient')),
        ('New Patient', _('New Patient')),
        ('Patient', _('Patient')),
    )

    first_name = models.CharField(_('First Name'), max_length=50)
    last_name = models.CharField(_('Last Name'), max_length=50)
    username = models.CharField(_('Username'), max_length=50, unique=True)
    ...
    # required
    is_patient = models.CharField(_('Patient'), max_length=20, choices=patient_status)
    ...

views.py adding appointment:

def add_appointment(request):
    form = AddAppointmentForm(request.POST or None)
    
    if request.method == 'POST':
        if form.is_valid():
            appoint_user = form.cleaned_data.get('user')
            appoint_seat = form.cleaned_data.get('seat')
            appoint_start_appointment = form.cleaned_data.get('start_appointment')
            appoint_end_appointment = form.cleaned_data.get('end_appointment')
            
            # If Appointment already exist 
            if Appointment.objects.filter(user=appoint_user, seat=appoint_seat, start_appointment=appoint_start_appointment, end_appointment=appoint_end_appointment).exists():
                messages.warning(request, "This appointment already exists.")

            else:
                form.save()

                messages.success(request, 'Appointment was added successfully!')
                return redirect('appointments:add_appointment')
    else:
        form = AddAppointmentForm()

I would like to update is_patient after is_valid(), something like:

patient = Appointment.objects.filter(user=appoint_user).count()
if patient > 0:
  patient.user__is_patient = 'Patient'
  patient.save()

How can i access is_patient from Account’s table in order to update and also where is the right place to put the code, in the view?

Update with appointments model

class Appointment(models.Model):
    
    APPOINTMENT_STATUS = (
        ('New', _('New')),
        ('Finished', _('Finished')),
        ('Rescheduled', _('Rescheduled')),
        ('Cancelled', _('Cancelled')),
        ('Notshow', _('Notshown')),
    )

    DURATION = (
        ('Notstarted', _('Not Started')),
        ('Checkin', _('Check In')),
        ('TransferToSeat', _('Transfer to Seat')),
        ('Completed', _('Completed')),
    )

    user = models.ForeignKey(Account, on_delete=models.CASCADE)
    seat = models.ForeignKey(Seat, on_delete=models.SET_NULL, null=True)
    start_appointment = models.DateTimeField(default=timezone.now, blank=True)
    end_appointment = models.DateTimeField(default=timezone.now, blank=True)
    name = models.CharField(max_length=255)
    appointment_notes = models.TextField(_('Appointment Notes'), max_length=1500, null=True, blank=True)
    status = models.CharField(_('Appointment Status'), max_length=20, choices=APPOINTMENT_STATUS, default='New')
    duration = models.CharField(_('Duration'), max_length=20, choices=DURATION, default='Not Started')
    confirmed = models.BooleanField(_('Confirmed'), default=False)
    emailed = models.BooleanField(_('Emailed'), default=False)
    date_created = models.DateTimeField(_('Date Created'), auto_now_add=True)
    date_updated = models.DateTimeField(_('Date Updated'), auto_now=True)

Update after adding code:

if request.method == 'POST':
        if form.is_valid():
            appoint_user = form.cleaned_data.get('user')
            appoint_seat = form.cleaned_data.get('seat')
            appoint_start_appointment = form.cleaned_data.get('start_appointment')
            appoint_end_appointment = form.cleaned_data.get('end_appointment')
            
            # If Appointment already exist 
            if Appointment.objects.filter(user=appoint_user, seat=appoint_seat, start_appointment=appoint_start_appointment, end_appointment=appoint_end_appointment).exists():
                messages.warning(request, "This appointment already exists.")

            else:
                patient = Appointment.objects.filter(user=appoint_user)
                if patient.count() > 0:
                    patient[0].user.is_patient = 'Patient'
                    patient.user.save()
                
                else:
                    form.save()

>Solution :

try this

patients = Appointment.objects.filter(user=appoint_user)
if patients.count() > 0:
  for patient in patients:
      patient.user.is_patient = 'Patient'
      patient.user.save()

or

patients = Appointment.objects.filter(user=appoint_user)
if patients.count() > 0:
    appoint_user.is_patient = 'Patient'
    appoint_user.save()