问题描述
在Django中，所有时间我都看到 DoesNotExist 像 db.models.fields.related.py 一样被提出。不是 django.core.exceptions 中定义的 ObjectDoesNotExist ，而只是 DoesNotExist 。该异常类在哪里定义，或者我没有完全理解异常？我已经检查了它是否有异常（至少不是我所知道的）。我显然很困惑。
All the time in Django I see DoesNotExist being raised like in db.models.fields.related.py. Not ObjectDoesNotExist which is defined in django.core.exceptions, but just DoesNotExist. Where is this exception class defined, or am I not fully understanding exceptions? I've checked that it's not in exceptions (at least not that I know of). I'm confused obviously.
注意：它也是免费的，作为模型子类实例的属性，例如self.someforeignkey.DoesNotExist。
Note: It also comes free, as an attribute of a model sub-class instance, like `self.someforeignkey.DoesNotExist. How is this possible?
推荐答案
DoesNotExist 已记录为：
因此您可以很好地使用，除了ObjectDoesNotExist：并捕获在 try 子句中可能引发的所有特定于模型的 DoesNotExist 异常，或使用除了SomeSpecificModel.DoesNotExist：，当您想更具体时。
so you can perfectly well use except ObjectDoesNotExist: and catch all the model-specific DoesNotExist exceptions that might be raised in the try clause, or use except SomeSpecificModel.DoesNotExist: when you want to be more specific.
如果您正在Django的源代码中寻找特定位置将该属性添加到模型类的位置，请参见，第34-37行：
If you're looking for the specific spot in Django's source code where this attribute is added to model classes, see here, lines 34-37:
# Create the class.
new_class = type.__new__(cls, name, bases, {'__module__': attrs.pop('__module__')})
new_class.add_to_class('_meta', Options(attrs.pop('Meta', None)))
new_class.add_to_class('DoesNotExist', types.ClassType('DoesNotExist', (ObjectDoesNotExist,), {}))
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