如下面代码，会根据实例ID获取实例对象，大家知道get的时候如果id不存在会出现异常，但是filter不会。
那么，请问大家，像类似这种情况是用get然后处理异常要好呢，还是filter来做好呢，哪种更规范？

def get_city_image(self, instance):
        if instance.city_id:
            try:
                city_image = City.objects.get(id=instance.city_id).image.url
                # city_image = City.objects.filter(id=instance.city_id).last().image.url
            except Exception, e:
                city_image = None
        else:
            city_image = None
        return city_image