Question

如何在我定义的类中使用in作为运算符__getitem__的前提下，重载运算符[]？

class myClass:
    def __init__(self):
        self.slots = [None]*5

    def __setitem__(self, key, data):
        self.set(key, data)

    def __getitem__(self,key):
        return self.get(key)

    def set(self, key, data):
        self.slots[key]=data

    def get(self,key):
        return self.slots[key]

s=myClass()
s[0]='first'
s[1]='second'
print(s[0])#<-------first
print(s.slots)#<----['first', 'second', None, None, None]

如何使用in这样实现该功能？

print(('second' in s))#<----True
print(('third' in s))#<-----False

Answer 1

in运算符将调用__contains__魔法。见https://docs.python.org/2/reference/datamodel.html#object.contains

Answer 2

如果您尝试，则无需这样做：

"second" in ["first", "second"]

它会像你想要的那样返回True

如何重载operator`in`？

2 个答案: