Question

根据下面的类，我试图制作一条允许实例化所有字段的狗，我试过了：

class Animal(object):
    def __init__(self, legs=4, animal_type='beast'):
        self.legs           = legs
        self.animal_type    = animal_type


class Dog(Animal):
    def __init__(self, name=None, owner=None):
        self.name   = name
        self.owner  = owner

dog = Dog(legs=4, animal_type='dog', name='Fido', owner='Bob')

print dog.owner
print dog.name

给了TypeError: __init__() got an unexpected keyword argument 'legs'

基于Initializing subclass variable in Python我试过

class Animal(object):
    def __init__(self, legs=4, animal_type='beast'):
        self.legs           = legs
        self.animal_type    = animal_type


class Dog(Animal):
    def __init__(self, legs=None, animal_type=None, name=None, owner=None):
        if legs:
            self.legs = legs
        if animal_type:
            self.animal_type = animal_type
        self.name   = name
        self.owner  = owner

dog = Dog(name='Fido', owner='Bob')

print dog.name

但是在这里，我有一只狗，但是腿和animal_type没有默认，事实上，它们根本没有设置（图片如下）。

这个例子可以制作一条有4条腿的狗，但我没有默认的能力，我必须给腿和类型，否则它不会创建：

class Animal(object):
    def __init__(self, legs=4, animal_type='beast'):
        self.legs           = legs
        self.animal_type    = animal_type


class Dog(Animal):
    def __init__(self, legs, animal_type, name=None, owner=None):
        if legs:
            self.legs = legs
        if animal_type:
            self.animal_type = animal_type
        self.name   = name
        self.owner  = owner

dog = Dog(4, 'dog', name='Fido', owner='Bob')

print dog.name

如果没有给出默认的父属性，我怎么能够子类化才能选择性地覆盖它们？所以我怎么能把这些类动物和狗，如果我不说腿或类型得到腿= 4的狗，和animal_type =野兽？谢谢

Answer 1

class Animal(object):
    def __init__(self, legs=4, animal_type='beast'):
        self.legs        = legs
        self.animal_type = animal_type


class Dog(Animal):
    def __init__(self, name=None, owner=None, **kwargs):
        super(Dog, self).__init__(**kwargs)
        self.name  = name
        self.owner = owner

dog = Dog(legs=4, animal_type='dog', name='Fido', owner='Bob')

在**kwargs中捕获额外的参数，并用它们调用父的构造函数。

在创建子类Python时初始化父类属性

1 个答案: