python - 我们可以向 super() 传递什么参数？

Question

我创建了一个 Vehicle 类，还想从它派生一个 Car 类，调用父构造函数来设置 name 和 颜色。但是我收到此错误:

super() takes at least 1 argument (0 given)

这是我的代码:

class Vehicle:

    def __init__(self, name, color):
        self.__name = name      # __name is private to Vehicle class
        self.__color = color

    def getColor(self):         # getColor() function is accessible to class Car
        return self.__color

    def setColor(self, color):  # setColor is accessible outside the class
        self.__color = color

    def getName(self):          # getName() is accessible outside the class
        return self.__name
        self.__model = model

    def getDescription(self):
        return self.getName() + self.__model + " in " + self.getColor() + " color"


class Car(Vehicle):

    def __init__(self, name, color, model):
        # call parent constructor to set name and color
        super().__init__(name,  color)
        self.__model = model

    def getDescription(self):
        return self.getName() + self.__model + " in " + self.getColor() + " color"

# in method getDescrition we are able to call getName(), getColor() because they are
# accessible to child class through inheritance

c = Car("Ford Mustang", "red", "GT350")
print(c.getDescription())

Answer 1

Python 3 - 不错

在 Python 3 中这是可行的:

class Vehicle:
    def __init__(self):
        print('Vehicle __init__() called')

class Car(Vehicle):
    def __init__(self):
        super().__init__()

car = Car()

打印:

Vehicle __init__() called

Python 2 - 更多工作

在 Python 2 中尝试同样的事情会导致问题:

class Vehicle:
    def __init__(self):
        print('Vehicle __init__() called')

class Car(Vehicle):
    def __init__(self):
        super().__init__()


car = Car()

抛出这个异常:

Traceback (most recent call last):
...
TypeError: super() takes at least 1 argument (0 given)

我们需要将自己的类作为第一个参数，并将 self 作为 super() 的第二个参数:

class Vehicle:
    def __init__(self):
        print('Vehicle __init__() called')

class Car(Vehicle):
    def __init__(self):
        super(Car, self).__init__()

car = Car()

但这还不够:

Traceback (most recent call last):
...
TypeError: must be type, not classobj

class Vehicle: 创建一个旧式类。 Vehicle 必须继承自 object 才能获得与 super() 一起使用的新型类:

class Vehicle(object):
    def __init__(self):
        print('Vehicle __init__() called')

class Car(Vehicle):
    def __init__(self):
        super(Car, self).__init__()

car = Car()

打印:

Vehicle __init__() called

在 Python 2 中没有参数的 super()

不得不一直记住这两个参数有点烦人。幸运的是，有一个解决方案。强烈推荐的图书馆Python-Future允许您在 Python 2 中使用不带参数的 super():

from builtins import object, super # from Python-Future

class Vehicle(object):
    def __init__(self):
        print('Vehicle __init__() called')

class Car(Vehicle):
    def __init__(self):
        super().__init__()

car = Car()

打印:

Vehicle __init__() called