>>> class Complex:
...     def __init__(self, realpart, imagpart):
...         self.r = realpart
...         self.i = imagpart
>>> x = Complex(3.0, -4.5)
>>> x.r, x.i
(3.0, -4.5)

class Dog:
    tricks = []             # mistaken use of a class variable
    def __init__(self, name):
        self.name = name
    def add_trick(self, trick):
        self.tricks.append(trick)
>>> d = Dog('Fido')
>>> e = Dog('Buddy')
>>> d.add_trick('roll over')
>>> e.add_trick('play dead')
>>> d.tricks                # unexpectedly shared by all dogs
['roll over', 'play dead']