python - 如何在 Python 中从继承的类中设置和获取父类属性？

Question

我有Family及其继承的Person类。如何familyName从类中获取属性Person？

class Family(object):
    def __init__(self, familyName):
        self.familyName = familyName

class Person(Family):
    def __init__(self, personName):
        self.personName = personName

例如，让这些Family和Person对象：

strauss = Family('Strauss')
johaness = Person('Johaness')
richard = Person('Richard')

我想做一些事情，例如：

print richard.familyName

并得到'Strauss'. 我怎样才能做到这一点？

Answer 1

你不能。

实例只继承父类的方法和属性，不继承实例属性。你不应该混淆这两者。

strauss.familyName是实例的实例属性Family。Person实例将拥有自己的familyName属性副本。

您通常会将Person构造函数编码为采用两个参数：

class Person(Family):
    def __init__(self, personName, familyName):
        super(Person, self).__init__(familyName)
        self.personName = personName

johaness = Person('Johaness', 'Strauss')
richard = Person('Richard', 'Strauss')

另一种方法是Person保存对Family实例的引用：

class Person(object):
    def __init__(self, personName, family):
        self.personName = personName
        self.family = family

wherePerson不再继承自Family. 像这样使用它：

strauss = Family('Strauss')
johaness = Person('Johaness', strauss)
richard = Person('Richard', strauss)

print johaness.family.familyName

Answer 2

除了 Martijns 的建议之外，您还可以从 Family 实例创建 Person，这样可以让家人跟踪其成员：

class Person(object):
    def __init__(self, person_name, family):
        self.person_name = person_name
        self.family = family

    def __str__(self):
        return ' '.join((self.person_name, self.family.family_name))

class Family(object):
    def __init__(self, family_name):
        self.family_name = family_name
        self.members = []

    def add_person(self, person_name):
        person = Person(person_name, self)
        self.members.append(person)
        return person

    def __str__(self):
        return 'The %s family: ' % self.family_name + ', '.join(str(x) for x in self.members)

像这样的用法：

>>> strauss = Family('Strauss')
>>> johannes = strauss.add_person('Johannes')
>>> richard = strauss.add_person('Richard')
>>> 
>>> print johannes
Johannes Strauss
>>> print richard
Richard Strauss
>>> print strauss
The Strauss family: Johannes Strauss, Richard Strauss