Please help! Problem with my Point object

[itrema]

Hello everyone! I am having a problem with my code and after minutes of search, I landed here. I need your help.

Here is the problem: We want to create a Point object capable of handling the most basic vector operations; we want our Point object to handle addition and subtraction. For two points (x1,y1)+(x2,y2)=(x1+x2,y1+y2) and similarly for subtraction. Implement a method within Point that allows two Point objects to be added together using the + operator, and likewise for subtraction.

Here is my code:

class Point(object):
    def __init__(self, x, y):
        self.x = x
        self.y = y
    def __repr__(self):
        return "Point({0}, {1})".format(self.x, self.y)
    def __add__(self, other):
        a = self.x + other.x
        b = self.y + other.y
        return "Point({a}, {b})"
    def __sub__(a, b):
        c = self.x - other.x
        d = self.y - other.y
        return "Point({c}, {d})"

And I've got type erreor.
Can anyone help me?
By the way if you have an idea for multiplication, I'll be....