Can you explain in this code how does self,other workd ?

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)

p=vector2D(5,2)
q=vector2D(7,9)
r=vector2D(5,0)

r=p+q+r
# r=p.__add__(q)
print("{}i + {}j".format(r.x,r.y))

Answer 1

self refers to the current object (left of the operator). other refers to another object (right of the operator). When doing p+q. p is this and q is other. What it returns is a vector2D(p.x+q.x, p.y+q.y)