Python 如何从子类调用基类的 __init__ 方法？

How to call Base Class's __init__ method from the child class?

提问by Prakhar Mohan Srivastava

If I have a python class as:

如果我有一个 python 类：

class BaseClass(object):
#code and the init function of the base class

And then I define a child class such as:

然后我定义了一个子类，例如：

class ChildClass(BaseClass):
#here I want to call the init function of the base class

If the init function of the base class takes some arguments that I am taking them as arguments of the child class's init function, how do I pass these arguments to the base class?

如果基类的 init 函数接受一些我将它们作为子类 init 函数的参数的参数，我该如何将这些参数传递给基类？

The code that I have written is:

我写的代码是：

class Car(object):
    condition = "new"

    def __init__(self, model, color, mpg):
        self.model = model
        self.color = color
        self.mpg   = mpg

class ElectricCar(Car):
    def __init__(self, battery_type, model, color, mpg):
        self.battery_type=battery_type
        super(ElectricCar, self).__init__(model, color, mpg)

Where am I going wrong?

我哪里错了？

采纳答案by Mingyu

You could use super(ChildClass, self).__init__()

你可以用 super(ChildClass, self).__init__()

class BaseClass(object):
    def __init__(self, *args, **kwargs):
        pass

class ChildClass(BaseClass):
    def __init__(self, *args, **kwargs):
        super(ChildClass, self).__init__(*args, **kwargs)

Your indentation is incorrect, here's the modified code:

您的缩进不正确，这是修改后的代码：

class Car(object):
    condition = "new"

    def __init__(self, model, color, mpg):
        self.model = model
        self.color = color
        self.mpg   = mpg

class ElectricCar(Car):
    def __init__(self, battery_type, model, color, mpg):
        self.battery_type=battery_type
        super(ElectricCar, self).__init__(model, color, mpg)

car = ElectricCar('battery', 'ford', 'golden', 10)
print car.__dict__

Here's the output:

这是输出：

{'color': 'golden', 'mpg': 10, 'model': 'ford', 'battery_type': 'battery'}

回答by thefourtheye

You can call the super class's constructor like this

您可以像这样调用超类的构造函数

class A(object):
    def __init__(self, number):
        print "parent", number

class B(A):
    def __init__(self):
        super(B, self).__init__(5)

b = B()

NOTE:

笔记：

This will work only when the parent class inherits object

这仅在父类继承时有效 object

回答by Manjunath Reddy

As Mingyu pointed out, there is a problem in formatting. Other than that, I would strongly recommend not using the Derived class's namewhile calling super()since it makes your code inflexible (code maintenance and inheritance issues). In Python 3, Use super().__init__instead. Here is the code after incorporating these changes :

正如明宇所指出的，格式有问题。除此之外，我强烈建议不要在调用时使用派生类的名称，super()因为它会使您的代码不灵活（代码维护和继承问题）。在 Python 3 中，super().__init__改为使用。这是合并这些更改后的代码：

class Car(object):
    condition = "new"

    def __init__(self, model, color, mpg):
        self.model = model
        self.color = color
        self.mpg   = mpg

class ElectricCar(Car):

    def __init__(self, battery_type, model, color, mpg):
        self.battery_type=battery_type
        super().__init__(model, color, mpg)

Thanks to Erwin Mayer for pointing out the issue in using __class__with super()

感谢 Erwin Mayer 指出__class__与 super() 一起使用的问题

回答by Erwin Mayer

If you are using Python 3, it is recommended to simply call super() without any argument:

如果您使用的是 Python 3，建议只调用 super() 而不带任何参数：

class Car(object):
    condition = "new"

    def __init__(self, model, color, mpg):
        self.model = model
        self.color = color
        self.mpg   = mpg

class ElectricCar(Car):
    def __init__(self, battery_type, model, color, mpg):
        self.battery_type=battery_type
        super().__init__(model, color, mpg)

car = ElectricCar('battery', 'ford', 'golden', 10)
print car.__dict__

Do not call super with classas it may lead to infinite recursion exceptions as per this answer.

不要用class调用 super，因为根据这个答案，它可能会导致无限递归异常。