class Number:
def __init__(self, v=0):
self.v = v
def __str__(self):
return str(self.v)
def __add__(self, x):
self.v += x
n = Number(3)
print(n)
n + 3
print(n)
type(n)
x = 3 # primitive int
x += 3
print(x)
type(x)