How work Magic Method ?

Question

class Vector2D:
def __init__(self, x, y):
self.x = x
self.y = y
def __add__(self, other):
return Vector2D(self.x + other.x, self.y + other.y)

first = Vector2D(5, 7)
second = Vector2D(3, 9)
result = first + second
print(result.x)
print(result.y)

Answer 1

In your example code, you have the __add__ method for the Vector2D class set. Anything within that function will run only when the class is being added to something else, with in this case it returning a new instance of the Vector2D class, with the x value being the addition of both x values of the classes being added and the y value being the y values of the classes being added.

In this case, you have the first variable being a new instance of the Vector2D class with the x value being 5 and the y value being 7, and the second variable being an instance where x = 3 and y = 9. Adding both first and second will result in a new instance of the Vector2D class being created and set in the result variable, where the new parameters are x = 8 (first.x = 5 and second.x = 3, so 5 + 3 = 8), and y = 16 (first.y = 7, second.y = 9, 7 + 9 = 16).