9.4.5 导入模块中的所有类
要导入模块中的每个类,可使用下面的语法:
from mod import *
不推荐使用这种导入方式,其原因有二。首先,如果只要看一下文件开头的import语句,就能清楚地知道程序使用了哪些类,将大有裨益;但这种导入方式没有明确地指出你
使用了模块中的哪些类。这种导入方式还可能引发名称方面的困惑。如果你不小心导入了一个与程序文件中其他东西同名的类,将引发难以诊断的错误。这里之所以介绍这种导
入方式,是因为虽然不推荐使用这种方式,但你可能会在别人编写的代码中见到它。
car.py代码如下:
"""A class that can be used to represent a car."""
class Car(object):
"""A simple attempt to represent a car."""
def __init__(self, manufacturer, model, year):
"""Initialize attributes to describe a car."""
self.manufacturer = manufacturer
self.model = model
self.year = year
self.odometer_reading = 0
def get_descriptive_name(self):
"""Return a neatly formatted descriptive name."""
long_name = str(self.year) + ' ' + self.manufacturer + ' ' + self.model
return long_name.title()
def read_odometer(self):
"""Print a statement showing the car's mileage."""
print("This car has " + str(self.odometer_reading) + " miles on it.")
def update_odometer(self, mileage):
"""
Set the odometer reading to the given value.
Reject the change if it attempts to roll the odometer back.
"""
if mileage >= self.odometer_reading:
self.odometer_reading = mileage
else:
print("You can't roll back an odometer!")
def increment_odometer(self, miles):
"""Add the given amount to the odometer reading."""
self.odometer_reading += miles
class Battery():
"""A simple attempt to model a battery for an electric car."""
def __init__(self, battery_size=60):
"""Initialize the batteery's attributes."""
self.battery_size = battery_size
def describe_battery(self):
"""Print a statement describing the battery size."""
print("This car has a " + str(self.battery_size) + "-kWh battery.")
def get_range(self):
"""Print a statement about the range this battery provides."""
if self.battery_size == 60:
range = 140
elif self.battery_size == 85:
range = 185
message = "This car can go approximately " + str(range)
message += " miles on a full charge."
print(message)
class ElectricCar(Car):
"""Models aspects of a car, specific to electric vehicles."""
def __init__(self, manufacturer, model, year):
"""
Initialize attributes of the parent class.
Then initialize attributes specific to an electric car.
"""
print "car ele\n"
super(ElectricCar,self).__init__(manufacturer, model, year)
self.battery = Battery()
