Operator Overloading in Python

class product:
    pq=0
    pw=0
    def __init__(self,q,w):
        self.w=w
        self.q=q
        product.pq=product.pq+q
        product.pw=product.pw+w

    def __add__(self,p):
        return product(self.q+p.q,self.w+p.w)

    def __sub__(self,p):
        return product(self.q-p.q,self.w-p.w)

    def displayProduct(self):
        return "Quantity = "+str(self.q)+" Weight = "+str(self.w)
    
p1=product(10,800)
print(p1.displayProduct())
p2=product(5,700)
print(p2.displayProduct())

p3=p1+p2
print(p3.displayProduct())

p4=p3-p1
print(p4.displayProduct())

print("Stock = ",product.pq,"  ",product.pw)