class Example:
  def __init__(self, number):
    self.number = number

  def __add__(self, other):
    return Example(self.number + other.number)

  def __sub__(self, other):
    return self.number - other.number
      
  def doSmth(self):
    print(self.number)

a = Example(7)
b = Example(42)

c = a + b
d = a - b

c.doSmth()
d.doSmth()