curriculum/challenges/english/blocks/learn-special-methods-by-building-a-vector-space/65f9dfd2e75e291a38695f13.md
Finally, return a new vector object. Use __class__ and unpack kwargs to instantiate the new vector.
You should return a new vector using __class__ and unpacking kwargs from the __sub__ method.
({
test: () => assert(runPython(`
_Node(_code).find_class("R2Vector").find_function("__sub__").has_return("self.__class__(**kwargs)")
`))
})
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})'
def __add__(self, other):
if type(self) != type(other):
return NotImplemented
kwargs = {i: getattr(self, i) + getattr(other, i) for i in vars(self)}
return self.__class__(**kwargs)
--fcc-editable-region--
def __sub__(self, other):
if type(self) != type(other):
return NotImplemented
kwargs = {i: getattr(self, i) - getattr(other, i) for i in vars(self)}
--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}')