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curriculum/challenges/english/blocks/learn-special-methods-by-building-a-vector-space/65f93acbb514857003510e79.md

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--description--

Declare a variable args and assign it the value returned by joining the elements in arg_list with the string ', '.

--hints--

You should declare a variable args and assign it the value returned by joining the elements in arg_list with the string ', '.

js
({ test: () => assert(runPython(`_Node(_code).find_class("R2Vector").find_function("__repr__").find_variable("args").is_equivalent("args = ', '.join(arg_list)")`)) })

--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)))
--fcc-editable-region--
    def __repr__(self):
        arg_list = [f'{key}={val}' for key, val in vars(self).items()]

--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}')