如何实现__eq__进行集合包含测试？

Question

我遇到了一个问题,我将一个实例添加到一个集合中,然后进行测试以查看该集合中是否存在该对象.我已经覆盖了__eq__()但是在包含测试期间它没有被调用.我必须改写__hash__()吗？如果是这样,我将如何实现,__hash__()因为我需要散列元组,列表和字典？

class DummyObj(object):

    def __init__(self, myTuple, myList, myDictionary=None):
        self.myTuple = myTuple
        self.myList = myList
        self.myDictionary = myDictionary

    def __eq__(self, other):
        return self.myTuple == other.myTuple and \
            self.myList == other.myList and \
            self.myDictionary == other.myDictionary

    def __ne__(self, other):
        return not self.__eq__(other)

if __name__ == '__main__':

    list1 = [1, 2, 3]
    t1    = (4, 5, 6)
    d1    = { 7 : True, 8 : True, 9 : True }
    p1 = DummyObj(t1, list1, d1)

    mySet = set()

    mySet.add(p1)

    if p1 in mySet:
        print "p1 in set"
    else:
        print "p1 not in set"

Answer 1

从集合的文档:

使用字典实现集合类.因此,对集合元素的要求与字典键的要求相同; 即,该元素定义__eq __()和__hash __().

所述__hash__函数文档表明异或部件的散列到一起.正如其他人所提到的,散列可变对象通常不是一个好主意,但如果你真的需要,这可行:

class DummyObj(object):

    ...

    def __hash__(self):
        return (hash(self.myTuple) ^
                hash(tuple(self.myList)) ^
                hash(tuple(self.myDictionary.items())))

并检查它是否有效:

p1 = DummyObj(t1, list1, d1)
p2 = DummyObj(t1, list1, d1)
mySet = set()
mySet.add(p1)

print "p1 in set", p1 in mySet
print "p2 in set", p2 in mySet

这打印:

$ python settest.py 
p1 in set True
p2 in set True