class Car(object):
    condition = "new"
    def __init__(self, model, color, mpg):
        self.model = model
        self.color = color
        self.mpg   = mpg
    def display_car(self):
        print "This is a %s %s with %s MPG." % (self.color, self.model, str(self.mpg))
    def drive_car(self):
        self.condition = "used"

class ElectricCar(Car):
    def __init__(self, model, color, mpg, battery_type):
        self.model = model
        self.color = color
        self.mpg   = mpg
        battery_type = battery_type

my_car = ElectricCar("DeLorean", "silver", 88, "molten salt")