高级编程技术（Python）作业9

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。

Solution：

class User():

    def __init__(self, first_name, last_name, age, login_attempts = 0):
        """initialize a user"""
        self.first_name = first_name
        self.last_name = last_name
        self.age = age
        self.login_attempts = login_attempts

    def describe_user(self):
        """show one's name"""
        print("My name is " + self.first_name.title() + 
              " " + self.last_name.title() + ".")
        print("I'm " + str(self.age) + " years old.")

    def greet_user(self):
        """say hallo to user"""
        print("Hello, " + self.first_name.title() + 
              " " + self.last_name.title() + "!")

    def increment_login_attempts(self):
        """increase login_attempts by 1"""
        self.login_attempts += 1

    def reset_login_attempts(self):
        """set login_attempts to 0"""
        self.login_attempts = 0

user1 = User("Tim", "Ashero", 21)
user1.describe_user()
user1.greet_user()
print()

user2 = User("xianghe", "li", 22)
user2.describe_user()
user2.greet_user()
user2.increment_login_attempts()
print(user2.login_attempts)
user2.increment_login_attempts()
print(user2.login_attempts)
user2.increment_login_attempts()
print(user2.login_attempts)
user2.reset_login_attempts()
print(user2.login_attempts)

Output：

My name is Tim Ashero.
I'm 21 years old.
Hello, Tim Ashero!

My name is Xianghe Li.
I'm 22 years old.
Hello, Xianghe Li!
1
2
3
0

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。

Solution：

class User():
    """build a user acount"""
    def __init__(self, first_name, last_name, age):
        """initialize a user"""
        self.first_name = first_name
        self.last_name = last_name
        self.age = age

    def describe_user(self):
        """show one's name"""
        print("My name is " + self.first_name.title() + 
              " " + self.last_name.title() + ".")
        print("I'm " + str(self.age) + " years old.")

    def greet_user(self):
        """say hallo to user"""
        print("Hello, " + self.first_name.title() + 
              " " + self.last_name.title() + "!")

class Admin(User):
    """build an admin acount"""
    def __init__(self, first_name, last_name, age):
        super().__init__(first_name, last_name, age)
        self.privileges = Privileges()

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

    def show_privileges(self):
        """print privilege"""
        for privilege in self.privileges:
            print(privilege)

admin1 = Admin("Ashero", "Tim", 21)
admin1.privileges.show_privileges()

Output：

can add post
can delete post
can ban user

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)

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。

Solution：

import random

class Die():
    """Make a die"""
    def __init__(self, sides = 6):
        """build by sides"""
        self.sides = sides

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

die6 = Die()
die10 = Die(10)
die20 = Die(20)

count = 10
while(count):
    print(10 - count + 1)
    print("6 sides: ", end = "")
    die6.roll_die()
    print("10 sides: ", end = "")
    die10.roll_die()
    print("20 sides: ", end = "")
    die20.roll_die()
    print()
    count -= 1

Output：

1
6 sides: 5
10 sides: 9
20 sides: 7

2
6 sides: 1
10 sides: 5
20 sides: 9

3
6 sides: 1
10 sides: 7
20 sides: 10

4
6 sides: 2
10 sides: 10
20 sides: 19

5
6 sides: 3
10 sides: 3
20 sides: 11

6
6 sides: 5
10 sides: 8
20 sides: 15

7
6 sides: 1
10 sides: 9
20 sides: 5

8
6 sides: 1
10 sides: 5
20 sides: 1

9
6 sides: 1
10 sides: 2
20 sides: 20

10
6 sides: 5
10 sides: 9
20 sides: 3