Python子类在构造函数中使用父变量

Question

So I'm working on a Text Based RPG and I have a class Item which looks like this:

class Item:
    def __init__(self, name, value):
        self.name = name
        self.value = value

Next I have a weapon class which I want to have inherit from the item class, and in the weapon constructor I want it to take the "name" and "value" variables. In my head it works like this:

class Weapon(Item):
    def __init(self, name, value, damage):
        self.damage = damage

Which I know is wrong, but that's essentially how I think it should work. I've looked up a bunch of threads on the "super()" function, but none of the explanations seem to be doing this. So is this something that's possible or should I just make the weapon class separate? Also... when it does work... what would the constructor call look like?

Answer 1

You can use it as follows inside your Weapon class:

class Weapon(Item):
    def __init__(self, name, value, damage):
        super(Weapon, self).__init__(name, value)
        self.damage = damage

And be sure to use new-style classes, ie inherit from object :

class Item(object):
    ...

Answer 2

Yes, calling the parent class's constructor is something that you usually need to do:

class Weapon(Item):
    def __init__(self, name, value, damage):
        # Initialize the Item part
        Item.__init__(self, name, value)

        # Initialize the Weapon-specific part
        self.damage = damage

As for making the weapon class separate—you should read through the article on composition over inheritance . People have varying opinions on whether inheritance is “right” and in which situations. Sorry that's so vague, but you haven't given that much information about your use case :-)