How do I add two vectors created by a class to eachother?

I have to add vector b to vector a. My class looks like this:

class Vector:
    """
    creates a vector, which can be indexed, changed and added to another vector.
    """
    def __init__(self,n=0,vec=[]):
        """
        creating vecor
        """
        self.n=n
        self.vec=list(vec)
        if len(vec)==0:
            for i in range(n):
                self.vec.append(0)
    def __getitem__(self,i):
        """
        indexing
        """
        if i>=len(self.vec):
            return(None)
        else:
            return(self.vec[i])
    def __setitem__(self,i,val):
        """
        changing
        """
        self.vec[i]=val

I tried adding another method to my class called add:

def add(a,b):
        """
        adds vector b to a
        """
        x=0
        for i in b:
            a[x]=a[x]+i
            x+=1
        return (a)
                

Lets say I want this to work:
a = Vector(vec = [1, 2, 3])
b = Vector(vec = [3, 4, 5])

c = Vector.add(a, b)

>Solution :

What it looks like you’re trying to do make a classmethod.

Something like this should work:

@classmethod
def add(cls, a,b):
    """
    adds vector b to a
    """
    return cls(vec=[x + y for x, y in zip(a.vec, b.vec)])