Learn Special Methods by Building a Vector Space - Step 26

Python
1

Tell us what’s happening:

I don’t understand what the error is here at all, please help!

Your code so far

import math


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

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

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


class R3Vector(R2Vector):
    def __init__(self, *, x, y, z):
        super().__init__(x=x, y=y)

# User Editable Region

        self.z = z


v1 = R2Vector(x=2, y=3)
v2 = R3Vector(x=2, y=2, z=3)

print(f'v1 = {v1.__str__()}')
print(f'v2 = {v2.__str__()}')


# User Editable Region

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/128.0.0.0 Safari/537.36

Challenge Information:

Learn Special Methods by Building a Vector Space - Step 26

2

What is the __str__ method and how is it used?

Why did we implement the __str__ method, what was the purpose?

1 Like
3

It is used to give a string representation of an object and here the purpose was to show the vector.

4

And in step 10, how did we use the __str__ method? It was a while ago:
https://www.freecodecamp.org/learn/scientific-computing-with-python/learn-special-methods-by-building-a-vector-space/step-10

5

ah, that’s right, I don’t need to use the . call to the str, brainfart xd thank you!

1 Like