week2 Mon

# In python, everything is an object from a class
# We can define our own classes

from math import sqrt

class Vector():
    # custom type for 2d vectors

    # class attribute shared by all objects of this class
    dim = 2
    
    def __init__(self, input_x, input_y):
        # constructor, called when new object is created, Vector(x,y)
        # self is the object being created
        # .x and .y are object attributes
        self.x = input_x
        self.y = input_y
    
    def length(self):
        # length method, returns length of vector
        l = sqrt(self.x**2+self.y**2)
        return l
    
    def scale(self, c):
        # method that scales the vector by a constant c
        # changes the object itself
        # no return value, so returns None
        self.x = self.x * c
        self.y = self.y * c

    def __repr__(self):
        # string representation of the object
        # without this method, it prints the memory address
        return f'({self.x},{self.y})'
            
    
    def add(self, other_vector):
        # method that adds another vector to this vector, returns new vector
        x_new = self.x + other_vector.x
        y_new = self.y + other_vector.y
        return Vector(x_new, y_new)
        
    def __add__(self, other_vector):
        # special method that overloads the + operator
        # without this method, vector + vector would raise an error
        x_new = self.x + other_vector.x
        y_new = self.y + other_vector.y
        return Vector(x_new, y_new)
    
    def normalize(self):
        # method that scales the vector to unit length
        # can call other methods of the same object
        l = self.length()
        self.scale(1/l)


        

v = Vector(3,4)
v.x
print(v.x)
v.normalize()
print(v.length())
print(v)

3

v = Vector(1,1)
w = Vector(2,3)

# custom add method
p = v.add(w)
print(p)

# this is actually calling the __add__ method
q = v + w
print(q)

None