class HauntedBus():
    """备受幽灵乘客折磨的校车"""

    def __init__(self, passengers=[]):
        self.passengers = passengers

    def pick(self, name):
        self.passengers.append(name)

    def drop(self, name):
        self.passengers.remove(name)

bus1 = HauntedBus(['Alice', 'Bill'])
print(bus1.passengers)
bus1.pick('Charlie')
bus1.drop('Alice')
print(bus1.passengers)
bus2 = HauntedBus()
bus2.pick('Carrie')
print(bus2.passengers)
bus3 = HauntedBus()
print(bus3.passengers)
bus3.pick('Dave')
print(bus2.passengers)
print(bus2.passengers is bus3.passengers)
print(bus1.passengers)
print(dir(HauntedBus.__init__))
print(vars(HauntedBus))
print(HauntedBus.__init__.__defaults__[0] is bus2.passengers)