《Python编程：从入门到实践》第九章练习题

《Python编程：从入门到实践》第九章练习题

9-1 餐馆

创建一个名为Restaurant 的类，其方法__init__() 设置两个属性：restaurant_name 和cuisine_type 。创建一个名 为describe_restaurant() 的方法和一个名为open_restaurant() 的方法，其中前者打印前述两项信息，而后者打印一条消息，指出餐馆正在营业。 根据这个类创建一个名为restaurant 的实例，分别打印其两个属性，再调用前述两个方法。

代码：

class Restaurant():
    def __init__(self, restaurant_name, cuisine_name):
        self.restaurant_name = restaurant_name
        self.cuisine_name = cuisine_name

    def describe_restaurant(self):
        print("\nRestaurant name: " + self.restaurant_name.title())
        print("Cuisine name: " + self.cuisine_name.title())

    def open_restaurant(self):
        print("\n" + self.restaurant_name.title() + " is opening")


restaurant = Restaurant('beijing restaurant', 'traditional food')
print(restaurant.restaurant_name + "," + restaurant.cuisine_name)
restaurant.describe_restaurant()
restaurant.open_restaurant()

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9-2 三家餐馆

根据你为完成练习9-1而编写的类创建三个实例，并对每个实例调用方法describe_restaurant() 。

代码：

class Restaurant:
    def __init__(self, restaurant_name, cuisine_name):
        self.restaurant_name = restaurant_name
        self.cuisine_name = cuisine_name

    def describe_restaurant(self):
        print("\nRestaurant name: " + self.restaurant_name.title())
        print("Cuisine name: " + self.cuisine_name.title())

    def open_restaurant(self):
        print("\n" + self.restaurant_name.title() + " is opening")


beijing_restaurant = Restaurant('beijing restaurant', 'beijing food')
lanzhou_restaurant = Restaurant('lanzhou restaurant', 'lanzhou food')
sichuan_restaurant = Restaurant('sichuan restaurant', 'sichuan food')

beijing_restaurant.describe_restaurant()
lanzhou_restaurant.describe_restaurant()
sichuan_restaurant.describe_restaurant()

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9-3 用户

创建一个名为User 的类，其中包含属性first_name 和last_name ，还有用户简介通常会存储的其他几个属性。在类User 中定义一个名 为describe_user() 的方法，它打印用户信息摘要；再定义一个名为greet_user() 的方法，它向用户发出个性化的问候。 创建多个表示不同用户的实例，并对每个实例都调用上述两个方法。

代码：

class User:
    def __init__(self, first, last, age, location):
        self.first_name = first
        self.last_name = last
        self.age = age
        self.location = location

    def describe_user(self):
        print("\nUser info:")
        name = self.last_name.title() + " " + self.first_name.title()
        print("\tName: " + name)
        print("\tAge: " + str(self.age))
        print("\tLocation: " + self.location.title())

    def greet_user(self):
        name = self.last_name.title() + " " + self.first_name.title()
        print("\nHi, " + name + "! Nice to see you again!")


zhangsan = User('san', 'zhang', 22, 'shanghai')
lisi = User('si', 'li', 33, 'beijing')
wangwu = User('wu', 'wang', 44, 'sichuan')

zhangsan.describe_user()
zhangsan.greet_user()
lisi.describe_user()
lisi.greet_user()
wangwu.describe_user()
wangwu.greet_user()
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9-4 就餐人数

在为完成练习9-1而编写的程序中，添加一个名为number_served 的属性，并将其默认值设置为0。根据这个类创建一个名为restaurant 的实例；打印有多少人在这家餐馆就餐过，然后修改这个值并再次打印它。

添加一个名为set_number_served() 的方法，它让你能够设置就餐人数。调用这个方法并向它传递一个值，然后再次打印这个值。

添加一个名为increment_number_served() 的方法，它让你能够将就餐人数递增。调用这个方法并向它传递一个这样的值：你认为这家餐馆每天可能接待的就餐人数。

代码：

class Restaurant:
    def __init__(self, restaurant_name, cuisine_name):
        self.restaurant_name = restaurant_name
        self.cuisine_name = cuisine_name
        self.number_served = 0

    def describe_restaurant(self):
        print("\nRestaurant name: " + self.restaurant_name.title())
        print("Cuisine name: " + self.cuisine_name.title())
        print("Number served: " + str(self.number_served))

    def open_restaurant(self):
        print("\n" + self.restaurant_name.title() + " is opening")

    def set_number_served(self, number):
        self.number_served = number
        print("Number served: " + str(self.number_served))

    def increment_number_served(self, number):
        self.number_served = number
        print("Number wanter to serve: " + str(self.number_served))


restaurant = Restaurant('beijing restaurant', 'traditional food')
print(restaurant.number_served)
restaurant.number_served = 10
print(restaurant.number_served)

restaurant.set_number_served(20)
restaurant.increment_number_served(30)
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9-5 尝试登录次数

在为完成练习9-3而编写的User 类中，添加一个名为login_attempts 的属性。编写一个名为increment_login_attempts() 的方法， 它将属性login_attempts 的值加1。再编写一个名为reset_login_attempts() 的方法，它将属性login_attempts 的值重置为0。

根据User 类创建一个实例，再调用方法increment_login_attempts() 多次。打印属性login_attempts 的值，确认它被正确地递增；然后，调用方 法reset_login_attempts() ，并再次打印属性login_attempts 的值，确认它被重置为0。

代码：

class User:
    def __init__(self, first, last, age, location):
        self.first_name = first
        self.last_name = last
        self.age = age
        self.location = location
        self.login_attempts = 0

    def describe_user(self):
        print("\nUser info:")
        name = self.last_name.title() + " " + self.first_name.title()
        print("\tName: " + name)
        print("\tAge: " + str(self.age))
        print("\tLocation: " + self.location.title())

    def greet_user(self):
        name = self.last_name.title() + " " + self.first_name.title()
        print("\nHi, " + name + "! Nice to see you again!")

    def increment_login_attempts(self):
        self.login_attempts += 1

    def reset_login_attempts(self):
        self.login_attempts = 0


user = User('san', 'zhang', 22, 'shanghai')
for i in range(10):
    user.increment_login_attempts()
print(user.login_attempts)
user.reset_login_attempts()
print(user.login_attempts)

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9-6 冰淇淋小店

冰淇淋小店是一种特殊的餐馆。 编写一个名为IceCreamStand 的类， 让它继承你为完成练习9-1或练习9-4而编写的Restaurant 类。 这两个版本的Restaurant 类都可以， 挑选你更喜欢的那个即可。 添加一个名为flavors 的属性，用于存储一个由各种口味的冰淇淋组成的列表。 编写一个显示这些冰淇淋的方法。创建一个IceCreamStand 实例， 并调用这个方法。

代码：

class Restaurant:
    def __init__(self, restaurant_name, cuisine_name):
        self.restaurant_name = restaurant_name
        self.cuisine_name = cuisine_name
        self.number_served = 0

    def describe_restaurant(self):
        print("\nRestaurant name: " + self.restaurant_name.title())
        print("Cuisine name: " + self.cuisine_name.title())
        print("Number served: " + str(self.number_served))

    def open_restaurant(self):
        print("\n" + self.restaurant_name.title() + " is opening")

    def set_number_served(self, number):
        self.number_served = number


class IceCreamStand(Restaurant):
    def __init__(self, restaurant_name, cuisine_name):
        super(IceCreamStand, self).__init__(restaurant_name, cuisine_name)
        self.flavors = ['chocolate', 'strawberry', 'vanilla']

    def show_flavors(self):
        print("\nDifferent flavors in " + self.restaurant_name.title() + ":")
        for flavor in self.flavors:
            print("\t" + flavor.title() + " IceCream")


icecreamStand = IceCreamStand('love live icecream', 'ice cuisine')
icecreamStand.show_flavors()

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9-7 管理员

管理员是一种特殊的用户。编写一个名为Admin 的类，让它继承你为完成练习9-3或练习9-5而编写的User 类。添加一个名为privileges 的属性，用于存储一个由字符串（如"can add post" 、“can delete post” 、“can ban user” 等）组成的列表。编写一个名为show_privileges() 的方法，它显示管理员的权限。创建一个Admin 实例，并调用这个方法。

代码：

class User:
    def __init__(self, first, last, age, location):
        self.first_name = first
        self.last_name = last
        self.age = age
        self.location = location
        self.login_attempts = 0

    def describe_user(self):
        print("\nUser info:")
        name = self.last_name.title() + " " + self.first_name.title()
        print("\tName: " + name)
        print("\tAge: " + str(self.age))
        print("\tLocation: " + self.location.title())

    def greet_user(self):
        name = self.last_name.title() + " " + self.first_name.title()
        print("\nHi, " + name + "! Nice to see you again!")

    def increment_login_attempts(self):
        self.login_attempts += 1

    def reset_login_attempts(self):
        self.login_attempts = 0


class Admin(User):
    def __init__(self, first, last, age, location):
        super().__init__(first, last, age, location)
        self.privileges = ["can add post", "can delete post", "can ban user"]

    def show_privileges(self):
        name = self.last_name.title() + " " + self.first_name.title()
        print("\nHello, " + name + "! You have the following privileges:")
        for privilege in self.privileges:
            print("\t" + privilege.title())


admin = Admin('liu', 'zhao', '18', 'chengdu')
admin.show_privileges()
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9-8 权限

编写一个名为Privileges 的类，它只有一个属性——privileges ，其中存储了练习9-7 所说的字符串列表。将方法show_privileges() 移到这个类中。在Admin 类中，将一个Privileges 实例用作其属性。创建一个Admin 实例，并使用方法show_privileges() 来显示其权限。

代码：

class Privileges:
    def __init__(self):
        self.privileges = ["can add post", "can delete post", "can ban user"]

    def show_privileges(self):
        print("You have the following privileges:")
        for privilege in self.privileges:
            print("\t" + privilege.title())


class User:
    def __init__(self, first, last, age, location):
        self.first_name = first
        self.last_name = last
        self.age = age
        self.location = location
        self.login_attempts = 0

    def describe_user(self):
        print("\nUser info:")
        name = self.last_name.title() + " " + self.first_name.title()
        print("\tName: " + name)
        print("\tAge: " + str(self.age))
        print("\tLocation: " + self.location.title())

    def greet_user(self):
        name = self.last_name.title() + " " + self.first_name.title()
        print("\nHi, " + name + "! Nice to see you again!")

    def increment_login_attempts(self):
        self.login_attempts += 1

    def reset_login_attempts(self):
        self.login_attempts = 0


class Admin(User):
    def __init__(self, first, last, age, location):
        super().__init__(first, last, age, location)
        self.privileges = Privileges()


admin = Admin('liu', 'zhao', '18', 'chengdu')
admin.privileges.show_privileges()
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9-9 电瓶升级

在本节最后一个electric_car.py版本中，给Battery 类添加一个名为upgrade_battery() 的方法。这个方法检查电瓶容量，如果它不是85，就将它设置为85。创建一辆电瓶容量为默认值的电动汽车，调用方法get_range() ，然后对电瓶进行升级，并再次调用get_range() 。你会看到这辆汽车的续航里程增加了。

代码：

class Battery:
    def __init__(self, battery_size=70):
        self.battery_size = battery_size

    def describe_battery(self):
        print("This car has a " + str(self.battery_size) + "-kwh battery.")

    def get_range(self):
        if self.battery_size == 70:
            range = 240
        elif self.battery_size == 85:
            range = 270

        message = "This car can go approximately " + str(range) + " miles on a full charge."
        print(message)

    def upgrade_battery(self):
        if self.battery_size != 85:
            self.battery_size = 85


class Car:
    def __init__(self, make, model, year):
        self.make = make
        self.model = model
        self.year = year
        self.odometer_reading = 0

    def get_descriptive_name(self):
        long_name = str(self.year) + ' ' + self.make + ' ' + self.model
        return long_name.title()

    def read_odometer(self):
        print("This car has " + str(self.odometer_reading) + " miles on it.")

    def update_odometer(self, mileage):
        if mileage >= self.odometer_reading:
            self.odometer_reading = mileage
        else:
            print("You can't roll back an odometer!")

    def increment_odometer(self, miles):
        self.odometer_reading += miles


class ElectricCar(Car):
    def __init__(self, make, model, year):
        super().__init__(make, model, year)
        self.battery = Battery()


my_car = ElectricCar('tesla', 'model s', '2022')
# print(my_car.get_descriptive_name())
# my_car.battery.describe_battery()
my_car.battery.get_range()
my_car.battery.upgrade_battery()
# my_car.battery.describe_battery()
my_car.battery.get_range()

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9-10 导入Restaurant类

将最新的Restaurant类存储在一个模块中。在另一个文件中，导入Restaurant类，创建一个Restaurant实例，并调用Restaurant的一个方法，以确认import 语句正确无误。

代码：

Restaurant.py：

class Restaurant:
    def __init__(self, restaurant_name, cuisine_name):
        self.restaurant_name = restaurant_name
        self.cuisine_name = cuisine_name
        self.number_served = 0

    def describe_restaurant(self):
        print("\nRestaurant name: " + self.restaurant_name.title())
        print("Cuisine name: " + self.cuisine_name.title())
        print("Number served: " + str(self.number_served))

    def open_restaurant(self):
        print("\n" + self.restaurant_name.title() + " is opening")

    def set_number_served(self, number):
        self.number_served = number



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from restaurant import Restaurant

restaurant = Restaurant('beijing restaurant', 'traditional food')
print(restaurant.restaurant_name + "," + restaurant.cuisine_name)
restaurant.describe_restaurant()
restaurant.open_restaurant()
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9-11 导入Admin类

以为完成练习9-8的工作为基础，将User，Privieges和Admin类存储在一个模块中，在创建一个文件，在其中创建一个Admin实例并对其调用方法show_privileges()，以确认一切都能正确的运行。

代码：

user_privileges_admin.py：

class Privileges:
    def __init__(self):
        self.privileges = ["can add post", "can delete post", "can ban user"]

    def show_privileges(self):
        print("\nYou have the following privileges:")
        for privilege in self.privileges:
            print("\t" + privilege.title())


class User:
    def __init__(self, first, last, age, location):
        self.first_name = first
        self.last_name = last
        self.age = age
        self.location = location
        self.login_attempts = 0

    def describe_user(self):
        print("\nUser info:")
        name = self.last_name.title() + " " + self.first_name.title()
        print("\tName: " + name)
        print("\tAge: " + str(self.age))
        print("\tLocation: " + self.location.title())

    def greet_user(self):
        name = self.last_name.title() + " " + self.first_name.title()
        print("\nHi, " + name + "! Nice to see you again!")

    def increment_login_attempts(self):
        self.login_attempts += 1

    def reset_login_attempts(self):
        self.login_attempts = 0


class Admin(User):
    def __init__(self, first, last, age, location):
        super().__init__(first, last, age, location)
        self.privileges = Privileges()
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from user_privileges_admin import Admin


admin = Admin('liu', 'zhao', '18', 'chengdu')
admin.privileges.show_privileges()

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9-12 多个模块

将User类存储在一个模块中，并将Privileges和Admin类存储在另一个模块中。在创建一个文件，在其中创建一个Admin实例，并对其调用方法show_privileges()，以确认一切都能正确的运行。

代码：

user.py：

class User:
    def __init__(self, first, last, age, location):
        self.first_name = first
        self.last_name = last
        self.age = age
        self.location = location
        self.login_attempts = 0

    def describe_user(self):
        print("\nUser info:")
        name = self.last_name.title() + " " + self.first_name.title()
        print("\tName: " + name)
        print("\tAge: " + str(self.age))
        print("\tLocation: " + self.location.title())

    def greet_user(self):
        name = self.last_name.title() + " " + self.first_name.title()
        print("\nHi, " + name + "! Nice to see you again!")

    def increment_login_attempts(self):
        self.login_attempts += 1

    def reset_login_attempts(self):
        self.login_attempts = 0


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privileges_admin.py：

from user import User


class Privileges:
    def __init__(self):
        self.privileges = ["can add post", "can delete post", "can ban user"]

    def show_privileges(self):
        print("\nYou have the following privileges:")
        for privilege in self.privileges:
            print("\t" + privilege.title())


class Admin(User):
    def __init__(self, first, last, age, location):
        super().__init__(first, last, age, location)
        self.privileges = Privileges()

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from privileges_admin import Admin


admin = Admin('liu', 'zhao', '18', 'chengdu')
admin.privileges.show_privileges()
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9-13 使用OrderedDict

在练习6-4中， 你使用了一个标准字典来表示词汇表。
请使用OrderedDict 类来重写这个程序， 并确认输出的顺序与你在字典中添加键—值对的顺序一致。

代码：

from collections import OrderedDict


vocabulary = OrderedDict()

vocabulary['accumulator'] = '累加器'
vocabulary['algorithm'] = '算法'
vocabulary['array'] = '数组'
vocabulary['branch'] = '分支'
vocabulary['breakpoint'] = '断点'

for word, meaning in vocabulary.items():
    print(word + ":" + meaning)
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9-14 骰子

模块random 包含以各种方式生成随机数的函数， 其中的randint() 返回一个位于指定范围内的整数， 例如， 下面的代码返回一个1~6内的整数：

from random import randint
x = randint(1, 6)
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请创建一个Die 类， 它包含一个名为sides 的属性， 该属性的默认值为6。
编写一个名为roll_die() 的方法， 它打印位于1和骰子面数之间的随机数。
创建一个6面的骰子， 再掷10次。 创建一个10面的骰子和一个20面的骰子， 并将它们都掷10次。

代码：

from random import randint


class Die:
    def __init__(self, sides=6):
        self.sides = sides

    def roll_die(self):
        x = randint(1, self.sides)
        print(x)


die_6 = Die()
print("\nThe results of a 6-sized die:")
for i in range(10):
    die_6.roll_die()

die_10 = Die(sides=10)
print("\nThe results of a 10-sized die:")
for i in range(10):
    die_10.roll_die()

die_20 = Die(sides=20)
print("\nThe results of a 20-sized die:")
for i in range(10):
    die_20.roll_die()
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9-15 Python Module of the Week

要了解Python标准库， 一个很不错的资源是网站Python Module of the Week。请访问http://pymotw.com/并查看其中的目录， 在其中找一个你感兴趣的模块进行探索， 或阅读模块collections 和random 的文档。

代码：

import time

print('The time is      :', time.ctime())
later = time.time() + 15
print('15 secs from now :', time.ctime(later))

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运行结果：