Limit a single record in model for Django App

model.py

class MyModel(models.Model):
    onefield = models.CharField('The field', max_length=100)
class MyModelAdmin(admin.ModelAdmin):
  def has_add_permission(self, request):
    # if there's already an entry, do not allow adding
    count = MyModel.objects.all().count()
    if count == 0:
      return True
    return False

def has_add_permission(self, request):
        base_add_permission = super(MyModelAdmin, self).has_add_permission(request)
        if base_add_permission:
            # if there's already an entry, do not allow adding
            count = MyModel.objects.all().count()
            if count == 0:
                return True
        return False

would be better