类与静态方法

Question

I'm new in Python (come from C#), trying to figure out how OOP works here. Started from very begining I try to implement Vector class. I want to have basis vectors (i, j, k) defined in Vector class. In C#, I can do this like that:

public class Vector
{
    // fields...
    public Vector(int[] array){
        //...
    }

    public static Vector i(){
        return new Vector(new int[1, 0, 0]);
    }
}

Exploring Python I found 2 ways how to implement this: using either @classmethod or @staticmethod :

class Vector:
    def __init__(array):
        #...

    @classmethod
    def i(self):
        return Vector([1, 0, 0])

Since I don't need to have access to any information inside the class, should I really use @classmethod ?

Answer 1

I think you've confused yourself with your naming of arguments a bit. The first argument a class method receives is the class itself, which would be Vector, for now, until you have a subclass. A class method would be implemented like this:

    @classmethod
    def i(cls):
        return cls([1, 0, 0])

Generally, an instance method (no decorator) calls its first argument self , which is the instance. A class method has cls , which is the class, which can be used to construct an instance. A static method takes no "extra" argument, so your other option, if you want to always return a Vector , is:

    @staticmethod
    def i():
        return Vector([1, 0, 0])