我正在尝试将我的 Django 项目从 Python 2.7/Django 1.11 迁移到 Python 3.7/Django 2.1。
我发现了一个问题,我想了解它的原因。
我的项目中有 3 个模型:
class DeviceModel(models.Model):
name = models.CharField(max_length=255)
pirsh = models.CharField(max_length=255)
def __str__(self):
return self.name + " - " + self.pirsh
class Device(models.Model):
created_at = models.DateTimeField(auto_now_add=True)
device_model = models.ForeignKey(DeviceModel, on_delete=models.CASCADE)
serial_number = models.CharField(max_length=255)
def __str__(self):
return self.device_model.name + " - " + self.device_model.pirsh + " - " \
+ self.serial_number
class DeviceTest(models.Model):
device = models.ForeignKey(Device, on_delete=models.CASCADE)
created_at = models.DateTimeField()
TEST_OK = '+'
TEST_ERROR = '-'
TEST_PENDING = '?'
TEST_RESULT_CHOICES = (
(TEST_OK, 'Success'),
(TEST_ERROR, 'Fail'),
(TEST_PENDING, 'Not checked'),
)
status = models.CharField(max_length=1, choices=TEST_RESULT_CHOICES, default=TEST_PENDING)
comment = models.TextField(blank=True, default="")
tester = models.CharField(max_length=255)
action = models.CharField(max_length=255)
def save(self, *args, **kwargs):
''' On save, update timestamps '''
if not self.created_at:
self.created_at = timezone.now()
return super(DeviceTest, self).save(*args, **kwargs)
def __str__(self):
return self.device_id.device_model.name + " - " + \
self.device_id.device_model.pirsh + " - " + \
self.device_id.serial_number + " - " + \
str(self.created_at) + " - " + \
"Result (" + self.status + ")"
这是我Device
按最新测试状态对对象进行排序的代码(“dev_filter”、“field”和“order”参数是从 GET 请求中解析的):
if (dev_filter!="") and (dev_filter!="-1"):
device_list = Device.objects.all().filter(device_model = dev_filter)
else:
device_list = Device.objects.all()
dev_status_list = []
for dev in device_list:
try:
dev_status_list.append(DeviceTest.objects.filter(device_id=dev.pk).latest('created_at').status)
except:
dev_status_list.append("Not checked")
device_list = [device_list for (dev_status_list, device_list) in sorted(zip(dev_status_list, device_list))]
if (order == '-'):
device_list.reverse()
此代码在 Python 2.7/Django 1.11 中运行良好,但在 Python 3.7/Django 2.1 中却不行
Django 标记为错误sorted(zip(dev_status_list, device_list))
函数:
TypeError: '<' not supported between instances of 'Device' and 'Device'
我看到了这个问题的两种解决方案:要么使用
device_list = [device_list for (dev_status_list, device_list) in sorted(zip(dev_status_list, device_list), key=lambda x: (x[0],x[1].__str__()))]
或向模型添加__lt__
方法:Device
def __lt__(self, other):
return self.__str__() < other.__str__()
我的问题是——改变了什么?这个错误是因为 Python 升级还是 Django 升级而发生的?Python 2.7/Django 1.11 框架中Device
对象的默认排序方法是什么?我是否正确,它是字符串表示?我的哪种解决方案更受欢迎?