class Thing:
  
  def __init__(self):
    self._a = 1
    self._b = 4

  def foo(self, param):
    self._a = self._a + param
    self._b = self._b + param
    return (self._a + self._b)

  def bar(self, param):
    a = self._a + param
    b = self._b + param
    return (a + b)

  def __str__(self):
    return 'a is '+str(self._a)+', b is '+str(self._b)


it = Thing()
print it.foo(2)
print it.bar(3)
print it