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curriculum/challenges/english/blocks/learn-special-methods-by-building-a-vector-space/65f9b486989cb90ff3e77ac8.md

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--description--

The other parameter of your __add__ method represents the operand placed at the right side of the + operator in an addition operation.

You want to verify that the right-hand operand is not an object of the same class as the left-hand operand (i.e. self). Create an if statement that verifies that by checking the type of the operands.

--hints--

You should create an if statement that checks if type(self) and type(other) are different.

js
({ test: () => assert(runPython(`
node = _Node(_code).find_class("R2Vector").find_function("__add__").find_ifs()[0].find_conditions()[0]
node.is_equivalent("type(self) != type(other)") or node.is_equivalent("type(other) != type(self)")
`)) })

--seed--

--seed-contents--

py
class R2Vector:
    def __init__(self, *, x, y):
        self.x = x
        self.y = y

    def norm(self):
        return sum(val**2 for val in vars(self).values())**0.5

    def __str__(self):
        return str(tuple(getattr(self, i) for i in vars(self)))

    def __repr__(self):
        arg_list = [f'{key}={val}' for key, val in vars(self).items()]
        args = ', '.join(arg_list)
        return f'{self.__class__.__name__}({args})'
--fcc-editable-region--
    def __add__(self, other):
        pass
--fcc-editable-region--
class R3Vector(R2Vector):
    def __init__(self, *, x, y, z):
        super().__init__(x=x, y=y)
        self.z = z

v1 = R2Vector(x=2, y=3)
v2 = R3Vector(x=2, y=2, z=3)
print(f'v1 = {v1}')
print(f'v2 = {v2}')