遗传缺失属性

Question

我得到一个错误，说类吉他没有属性“类型”，但它应该继承自超级类设备。在

class Equipment(object):
    __id = 0
    __type = 0
    __brand = 0
    __model = 0
    __serialNumber = 0
    __purchaseCost = 0
    __hireCost = 0
    __available = 0

    def __init__(self, type, brand, model, serialNumber, purchaseCost, hireCost, available):
        self.__type = type
        self.__brand = brand
        self.__model = model
        self.__serialNumber = serialNumber
        self.__purchaseCost = purchaseCost
        self.__hireCost = hireCost
        self.__available = available

    def get_type(self):
        return self.__type
    def set_type(self,type):
        self.__type = type

    def get_brand(self):
        return self.__brand
    def set_brand(self,brand):
        self.__brand = brand

    def get_model(self):
        return self.__brand
    def set_model(self,model):
        self.__model = model

    def get_serialNumber(self):
        return self.__serialNumber
    def set_serialNumber(self,serialNumber):
        self.__serialNumber = serialNumber

    def get_purchaseCost(self):
        return self.__purchaseCost
    def set_purchaseCost(self,purchaseCost):
        self.__purchaseCost = purchaseCost

    def get_hireCost(self):
        return self.__hireCost
    def set_hireCost(self,hireCost):
        self.__hireCost = hireCost

    def get_available(self):
        return self.__available
    def set_available(self,available):
        self.__available = available

    def toString(self):
        return "type : {}, brand : {}, model : {}, serial number : {}, purchase cost : {}, hire cost : {}, available : {}".format(self.__type,
                                                        self.__brand,
                                                        self.__model,
                                                        self.__serialNumber,
                                                        self.__purchaseCost,
                                                        self.__hireCost,
                                                        self.__available)           
class Guitar(Equipment):
    __subtype = 0
    __bodyType = 0
    __pickupType = 0
    __tremSystem = 0

    def __init__(self, type, brand, model, serialNumber, purchaseCost, hireCost, available, subtype, bodyType, pickupType, tremSystem):
        super(Guitar, self).__init__(type, brand, model, serialNumber, purchaseCost, hireCost, available)
        self.__subtype = subtype
        self.__bodyType = bodyType
        self.__pickupType = pickupType
        self.__tremSystem = tremSystem


    def get_subtype(self):
        return self.__subtype
    def set_subtype(self, subtype):
        self.__subtype = subtype

    def get_bodyType(self):
        return self.__bodyType
    def set_bodyType(self, bodyType):
        self.__bodyType = bodyType

    def get_pickupType(self):
        return self.__pickupType
    def set_pickupType(self, pickupType):
        self.__pickupType = pickupType

    def get_tremSystem(self):
        return self.__tremSystem
    def set_tremSystem(self, tremSystem):
        self.__tremSystem = tremSystem

    def toString(self):
        return "type : {}, subtype : {}, brand : {}, model : {}, serial number : {}, purchase cost : {}, hire cost : {}, available : {}, body type : {}, pickup type : {}, trem system : {}".format(self.__type,
                                self.__subtype,
                                self.__brand,
                                self.__model,
                                self.__serialNumber,
                                self.__purchaseCost,
                                self.__hireCost,
                                self.__available,
                                self.__bodyType,
                                self.__pickupType,
                                self.__tremSystem)  

def main():
    type = input("please enter type: ")
    brand = input("please enter brand: ")
    model = input("please enter model: ")
    serialNumber = input("please enter serial number: ")
    purchaseCost = input("please enter purchase cost: ")
    hireCost = input("please enter hire cost: ")
    available = input("is item available: ")

    if type == "guitar":
        subtype = input("please enter subtype: ")
        bodyType = input("please enter body type: ")
        pickupType = input("please enter pickup config: ")
        tremSystem = input("please enter trem system: ")


    guitar = Guitar(type, brand, model, serialNumber, purchaseCost, hireCost, available, subtype, bodyType, pickupType, tremSystem)

    print(guitar.toString())

main()

我对设备类也做了同样的处理，所以我认为这肯定是一个继承的问题。在

Answer 1

在所有属性名前面加上两个下划线。这将触发一个名称混乱机制，该机制将类名添加到属性名中，因此子类无法重写它们。这是设计的，旨在避免意外的重写（类似于Java中的“private final”）

所以解决办法就是去掉这些下划线。Python没有真正的访问限制机制（更接近上面解释的名称混乱），它依赖于一个简单的命名约定：带有一个单个前导下划线的名称被视为“不是公共api的一部分”（相当于其他语言中的“protected”），所以这可能就是您想要的。在

尽管如此，你甚至不需要这个。Python对计算属性有很强的支持，因此您可以删除所有的getter/setter并使用普通属性，如果需要，您可以随时选择将它们转换为计算属性。在

Answer 2

当在类中定义一个变量时，变量前面有两个下划线，末尾有atmost一个下划线，这会导致python在定义类时执行名称混乱。在

这是一个类似-__type被转换为_<className>__type的名称。从documentation-

Since there is a valid use-case for class-private members (namely to avoid name clashes of names with names defined by subclasses), there is limited support for such a mechanism, called name mangling. Any identifier of the form __spam (at least two leading underscores, at most one trailing underscore) is textually replaced with _classname__spam, where classname is the current class name with leading underscore(s) stripped.

显示此行为的示例-

>>> class CA:
...     def __init__(self):
...             self.__type = 1
...
>>> c = CA()
>>> c.__type
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'CA' object has no attribute '__type'
>>> c._CA__type
1

让我们假设示例-__type，然后您就不能使用__type访问类外部的变量，当它被继承时，它将被继承为_<ClassName>__type。在

即使在继承过程中，同样的规则也适用

^{pr2}$

但从外观上看，不确定您是否真的需要定义clas中的所有名称，以使名称混乱发生。如果不需要名称损坏，请删除起始双下划线。在

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另外，当您直接在类中定义变量时，它们将成为类变量，即所有实例共享同一引用，直到您将每个实例的引用设置为不同的对象（通过赋值）。在您的例子中，不需要将所有变量定义为类变量。在