curriculum/challenges/english/blocks/learn-special-methods-by-building-a-vector-space/65f9b9710cca621244d3bde1.md
In Python, NotImplemented is a special value used to indicate that an operation is not implemented for a specific case.
NotImplemented does not raise an exception immediately. Instead, it signals to ask to the other operand how to perform the operation. If the request cannot be satisfied, a TypeError is returned by default.
Because you want to be able to sum two vectors only if they belong to the same class, return NotImplemented from the if statement you created in the previous step.
You should return NotImplemented from within the if body.
({ test: () => assert(runPython(`_Node(_code).find_class("R2Vector").find_function("__add__").find_ifs()[0].find_bodies()[0].has_return("NotImplemented")`)) })
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):
if type(self) != type(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}')