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python - Django：非主外键对象无法访问相关模型实例

问题描述

我是 Django 的新手。我在 models.py 中有2 类tech_system和设备

class tech_system(models.Model):
    id_tech_system = models.BigAutoField(db_column='ID_tech_system', primary_key=True)
    system_descript_short = models.CharField(max_length=255, blank=True, null=True)
    #More field here
    tech_system_code = models.CharField(unique=True, max_length=40)

    class Meta:
        managed = False
        db_table = 'tech_system'
        
    def __str__(self):
        return self.system_descript_short

        
class equiptment(models.Model):
    id_thietbi = models.BigAutoField(db_column='ID_thietbi', primary_key=True)
    tech_system_code = models.ForeignKey('tech_system', models.DO_NOTHING, db_column="tech_system_code", blank=True, null=True)

    class Meta:
        managed = False
        db_table = 'equiptment'

我使用python shell，设备模型对象无法访问相关的tech_system模型实例。我得到错误匹配查询不存在。我想得到值obj1.equiptment.tech_system_code.system_descript_short。我能怎么做？

谢谢你。

>>> obj1 = equiptment.objects.first()
>>> obj1.tech_system_code_id
'530'
>>> obj1.tech_system_code
Traceback (most recent call last):
  File "D:\Dev1\env1\lib\site-packages\django\db\models\fields\related_descriptors.py", line 173, in __get__
    rel_obj = self.field.get_cached_value(instance)
  File "D:\Dev1\env1\lib\site-packages\django\db\models\fields\mixins.py", line 15, in get_cached_value
    return instance._state.fields_cache[cache_name]
KeyError: 'tech_system_code'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "D:\Dev1\env1\lib\site-packages\django\db\models\fields\related_descriptors.py", line 187, in __get__
    rel_obj = self.get_object(instance)
  File "D:\Dev1\env1\lib\site-packages\django\db\models\fields\related_descriptors.py", line 154, in get_object
    return qs.get(self.field.get_reverse_related_filter(instance))
  File "D:\Dev1\env1\lib\site-packages\django\db\models\query.py", line 437, in get
    self.model._meta.object_name
app.models.tech_system.DoesNotExist: tech_system matching query does not exist.

标签： pythondjangoforeign-keys

解决方案

我发现 tech_system_code 记录被分配为 str 类型，而不是设备模型中的对象。导入数据库的记录值不正确。谢谢你的帮助。

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