Django：“ DoesNotExist”在哪里？来自？ [英] Django: Where does "DoesNotExist" come from?

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 已记录为此处：

DowsNotExist异常从
继承
django.core.exceptions.ObjectDoesNotExist，
，因此您可以定位多个
didNotExist异常。

The DoesNotExist exception inherits from django.core.exceptions.ObjectDoesNotExist, so you can target multiple DoesNotExist exceptions.

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，请参见此处，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,), {}))

这篇关于Django：“ DoesNotExist”在哪里？来自？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！