列表和集合的成员资格测试有何不同？
我无法弄清楚为什么第一个断言没问题，而第二个断言却引发错误。
subject_list = [Subject("A"), Subject("B"), Subject("C")]
subject_set = set()
subject_set.add(Subject("A"))
subject_set.add(Subject("B"))
subject_set.add(Subject("C"))
self.assertIn(Subject("A"), subject_list)
self.assertIn(Subject("A"), subject_set)
错误如下：
Traceback (most recent call last):
File "C:\Users\...\testSubject.py", line 34, in testIn
self.assertIn(Subject("A"), subject_set)
AssertionError: <Subject: A> not found in set([<Subject: B>, <Subject: C>, <Subject: A>])
Subject 类中的相等性测试只是 self.name == other.name，而在另一个 UnitTest 中，我验证 Subject("A") == subject （“A”）。我真的不明白为什么该主题在列表中而不是在集合中。理想情况下，我希望主题同时存在于两者中。
I'm having trouble with figuring out why the first of these assertions is OK and the second raises an error.
subject_list = [Subject("A"), Subject("B"), Subject("C")]
subject_set = set()
subject_set.add(Subject("A"))
subject_set.add(Subject("B"))
subject_set.add(Subject("C"))
self.assertIn(Subject("A"), subject_list)
self.assertIn(Subject("A"), subject_set)
Here is the error:
Traceback (most recent call last):
File "C:\Users\...\testSubject.py", line 34, in testIn
self.assertIn(Subject("A"), subject_set)
AssertionError: <Subject: A> not found in set([<Subject: B>, <Subject: C>, <Subject: A>])
The test for equality in the Subject class is simply self.name == other.name, and in another UnitTest I verify that Subject("A") == Subject("A") . I really can't figure out why the subject is in the list and not in the set. Ideally I'd like the subject to be in both.
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该表达式
将使用
Subject.__eq__()方法将Subject("A")与subject_list中的每个条目进行比较。如果不覆盖此方法，则默认情况下始终返回False，除非两个操作数是同一对象。如果Subject缺少__eq__()方法，上面的表达式将始终返回False，因为Subject("A")> 是一个新实例，不能已在列表中。相反的表达式
将首先使用
Subject.__hash__()来查找正确的存储桶，然后才使用Subject.__eq__()。如果您没有以与Subject.__eq__()兼容的方式定义Subject.__hash__()，则此操作将会失败。The expression
will compare
Subject("A")to each entry insubject_listusing theSubject.__eq__()method. If this method is not overwritten, it defaults to always returnFalseunless the two operands are the same object. The above expression would always returnFalseifSubjectlacked a__eq__()method, sinceSubject("A")is a new instance which cannot already be in the list.The expression
on the contrary will use
Subject.__hash__()first to find the right bucket, and useSubject.__eq__()only after this. If you did not defineSubject.__hash__()in a way compatible withSubject.__eq__(), this will fail.集合中的成员资格还取决于对象的哈希，因此您必须在类上适当地实现 __hash__() 方法。
Membership in a set also depends on the object's hash, and as such you must implement the
__hash__()method on the class appropriately.要么您的
Subject类中没有__hash__()方法，要么它是不可靠的。试试这个：文档位于此处。
Either you don't have a
__hash__()method in yourSubjectclass, or it is dodgy. Try this:The docs are here.
要在集合中使用它们，您必须确保
Subject可以正确散列。如果您自己没有定义__hash__，它只会采用id，并且对于不同的实例来说这是不同的。__hash__的定义应使相同的对象具有相同的哈希值。To use these in a set, you have to make sure
Subjectis properly hashable. If you do not define__hash__yourself, it will simply take theid, and that is different for different instances.__hash__should be defined such that equal objects have equal hashes.