在python2.7中，如何重写子类中的属性，同时维护超类的方法？

Question

我想在我的子类中继承一个属性，但我想从超类中调用一个方法。你知道吗

但是，为了从父级继承属性，我需要对其调用super。但是当我对它调用super时，它会从超类而不是子类中为它提供属性。如何确保它获得我在定义子类时分配给它的属性？你知道吗

class SuperClass2(object):
    def __init__(self, passed_in):
        self.attribute = 4
        self.passed_in = passed_in
        self.shared_method()

    def shared_method(self):
        assert self.passed_in == self.attribute, ' sorry they are not equal '

class SubClass2(SuperClass2):
    def __init__(self, passed_in):
        self.attribute = 3  # i set attribute to 3 here
        self.passed_in = passed_in
        super(SubClass2, self).__init__(passed_in)  # I already set attribute to 3 ....but gets overwritten when I call super

在上面的例子中，child=SubClass2(3)产生AssertionError: sorry they are not equal。你知道吗

正如您在上面的示例中所看到的，它将不允许我通过将属性设置为3来定义属性。如何重写子类中的属性，但维护超类的方法？你知道吗

Answer 1

方法1

最明显的是先调用super()，然后修改属性

class SubClass2(SuperClass2):
  def __init__(self, passed_in):
    super(SubClass2, self).__init__(passed_in)
    self.attribute = 3  # i set attribute to 3 here
    self.passed_in = passed_in

方法2

始终将这些公共属性委托给超类，因此如下所示：

class SuperClass2(object):
    def __init__(self, passed_in, attribute=4):
        self.attribute = attribute
        self.passed_in = passed_in
        self.shared_method()

    def shared_method(self):
        assert self.passed_in == self.attribute, ' sorry they are not equal '

class SubClass2(SuperClass2):
    def __init__(self, passed_in):
        super(SubClass2, self).__init__(passed_in=passed_in, attribute=3) 

方法3

将初始化委托给一个单独的方法，然后在子类中重写该方法

class SuperClass2(object):
    def __init__(self, passed_in):
        self._init(passed_in)
        self.shared_method()

    def _init(passed_in):
        self.attribute = 4
        self.passed_in = passed_in

    def shared_method(self):
        assert self.passed_in == self.attribute, ' sorry they are not equal '

class SubClass2(SuperClass2):
    def __init__(self, passed_in):
        super(SubClass2, self).__init__(passed_in=passed_in) 

    def _init(passed_in):
        self.attribute = 3
        self.passed_in = passed_in