class Vehicle:    def __init__(self, speed):        self.speed = speed    def drive(self, distance):        print 'need %f hour(s)' % (distance / self.speed)class Bike(Vehicle):#开始执行    passclass Car(Vehicle):    def __init__(self, speed, fuel):        Vehicle.__init__(self, speed)        self.fuel = fuel    def drive(self, distance):        Vehicle.drive(self, distance)        print 'need %f fuels' % (distance * self.fuel)b = Bike(15.0)c = Car(80.0,1.12)c.drive(200.0)