# Learn Special Methods by Building a Vector Space - Step 53

### Tell us what’s happening:

My code doesn’t pass. I’m not sure if I am using the correct methods. The instructions are quite hard to understand.

### Your code so far

``````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})'

if type(self) != type(other):
return NotImplemented
kwargs = {i: getattr(self, i) + getattr(other, i) for i in vars(self)}
return self.__class__(**kwargs)

def __sub__(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)

# User Editable Region

def __mul__(self, other):
if type(other) in (int, float):
kwargs = {i: getattr(self, i) * other for i in vars(self)}
return self.__class__(**kwargs)
elif isinstance(other, self.__class__):
pass

# User Editable Region

elif isinstance(type(other), self.__class__):
pass
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 = R2Vector(x=0.5, y=1.25)
print(f'v1 = {v1}')
print(f'v2 = {v2}')
v3 = v1 + v2
print(f'v1 + v2 = {v3}')
v4 = v1 - v2
print(f'v1 - v2 = {v4}')

``````

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### Challenge Information:

Learn Special Methods by Building a Vector Space - Step 53

You seem to have some extra code in there, but the first `elif` seems correct to me, although it also does not pass for me.

I got it, use the same method that you use in the `def __add__(self, other):` method:

``````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)
``````
1 Like

I don’t seem to understand. What do I add for the code to pass?

Hi @cjstaz13!

The instructions is looking for you to compare your two parameters of `__mul__` to see if they are the same Class/type.

As @pkdvalis is pointing out, you did this with `__sub__` and `__add__` before. However, you were comparing to see if they were not equal (`!=`) to the same Class/type.

Look back at your code. You’ve done this before. You’re just putting it in an `elif` now, and using the is equal to operator (`==`).

For the code inside the `elif`, use `pass`. It looks like you add more in the next step.

I hope this helps. Happy Coding!

Use `type()`, not `isinstance()`

I think both are correct but the tests require `type()`