Django比较模型实例的相等性 [英] Django comparing model instances for equality

问题描述

我明白，在单身情况下，您可以执行以下操作：

I understand that, with a singleton situation, you can perform such an operation as:

spam == eggs

如果垃圾邮件和蛋是具有所有相同属性值的同一类的实例，它将返回 True 。在Django模型中，这是很自然的，因为模型的两个独立实例不会一样，除非它们具有相同的 .pk 值。

and if spam and eggs are instances of the same class with all the same attribute values, it will return True. In a Django model, this is natural because two separate instances of a model won't ever be the same unless they have the same .pk value.

这样做的问题是，如果对实例的引用具有已被中间件更新到某处的属性，并且尚未保存，并且您尝试使用另一个当变量保存对同一模型的实例的引用时，它将返回 False ，因为它们对某些属性具有不同的值。显然我不需要像单身人士这样的东西，但是我想知道是否有一些官方的Djangonic（ha，一个新词）方法，或者如果我应该简单地检查 .pk 的值是否相同：

The problem with this is that if a reference to an instance has attributes that have been updated by middleware somewhere along the way and it hasn't been saved, and you're trying to it to another variable holding a reference to an instance of the same model, it will return False of course because they have different values for some of the attributes. Obviously I don't need something like a singleton , but I'm wondering if there some official Djangonic (ha, a new word) method for checking this, or if I should simply check that the .pk value is the same with:

spam.pk == eggs.pk

对不起如果这是一个巨大的浪费时间，但它似乎可能会有一个这样做的方法，我失踪的东西，如果我没有找到，我会后悔的路。

I'm sorry if this was a huge waste of time, but it just seems like there might be a method for doing this, and something I'm missing that I'll regret down the road if I don't find it.

你应该忽略这个问题的第一部分，因为你不应该比较单身与 == ，而是是。单身人士真的与这个问题无关。

You should disregard the first part of this question, since you shouldn't compare singletons with ==, but rather with is. Singletons really have nothing to do with this question.

推荐答案

从 django文档：

要比较两个模型实例，只需使用标准的Python比较运算符，double等于sign = ==。在幕后，比较了两个模型的主键值。

To compare two model instances, just use the standard Python comparison operator, the double equals sign: ==. Behind the scenes, that compares the primary key values of two models.

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