如何使用super（）初始化python中的子类参数

Question

I have seen various examples on How to use 'super' in python , but in all of these examples, there are no arguments being passed to the subclass' init method. Consider the following example.

Here is the base class:

class Animal(object):

    def __init__(self, genus):
        self.genus = genus

Now heres without using super:

class Dog(Animal):

    def __init__(self, genus):
        Animal.__init__(self, genus)


x = Dog('Canis')
print x.genus  # Successfully prints "Canis"

Now when I use super instead:

class Dog(Animal):

    def __init__(self, genus):
        super(Animal, self).__init__(genus)

x = Dog('Canis')
print x.genus  

I get the following error:

TypeError: object.__init__() takes no parameters

So then if object. init () takes no parameters, how to I set the specific genus of this particular animal when instantiated that subclass? Do I have to explicitly assign the variables like this:

class Dog(Animal):

    def __init__(self, genus):
        super(Animal, self).__init__()
        self.genus = genus

Answer 1

The fix

Write:

class Dog(Animal):

    def __init__(self, genus):
        super(Dog, self).__init__(genus)

So instead of:

super(Animal, self).__init__(genus)

use:

super(Dog, self).__init__(genus)

Think of: What is the super class of Dog ? Animal would be the right answer to this questions for this case. But if you use multiple inheritance this can be different.

Python 3 for the rescue

If you use Python 3, all things get simpler:

class Dog(Animal):

    def __init__(self, genus):
        super().__init__(genus)

works. Much less surface for making a mistake.

Python 3 niceties in Python 2 with Python-Future

If you need to work with Python 2, consider Python-Future . Than you can do this on Python 2:

from builtins import object, super

class Animal(object):

    def __init__(self, genus):
        self.genus = genus

class Dog(Animal):

    def __init__(self, genus):
        super().__init__(genus)

x = Dog('Canis')
print(x.genus)  

This builtins module comes from Python-Future. Using it, allows you to program Python 3 in Python 2 (at least for all important changes).