madsr

  class A:
    a = (1,)
    b = [1,]
    def __init__(self):
      self.a = (1,)
      self.b = [1,]

  A.a # this is the class attribute
    (1,)
  A.b # class attribute
    [1]
  obj = A()
  obj.a # instance attribute
    (1,)
  obj.b
    [1]
  obj.a += (2,)
  obj.b += [2,]
  A.a 
    (1,) # still the same class attribute
  A.b
    [1]
  obj.a
    (1, 2) # instance attribute appended
  obj.b
    [1, 2]