class Exc(models.Model):
        shipping_nr = models.CharField(max_length=15, )
        status = models.TextField(null=True, blank=True)
        added = models.DateTimeField(default=datetime.now())
        last_change = models.DateTimeField(default=datetime.now())
        class Meta:
                verbose_name_plural = 'Exc'
        def save(self, *args, **kwargs):
                if self.shipping_nr is not None:
                        self.status = get_status(self.shipping_nr)
                        self.last_change = datetime.now()
        models.Model.save(self,*args, **kwargs)