filename = 'A-Case-of-Sunburn.txt'
with open(filename) as f_obj:
    string = f_obj.read()

num = string.lower().count('the')
print(filename + ' include ' + str(num) + " 'the'.")

10-11 喜欢的数字：编写一个程序，提示用户输入他喜欢的数字，并使用json.dump()将这个数字存储到文件中。再编写一个程序，从文件中读取这个值，并打印消息”I know your favorite number! It's____.“。

import json

favorite_num = input("Enter your favorite number: ")

filename = 'favorite number.json'
with open(filename, 'w') as f_obj:
    json.dump(favorite_num, f_obj)

with open(filename) as f_obj:
    number = json.load(f_obj)

print("I know your favorite number! It's " + number + ".")

10-12 记住喜欢的数字：将10-11中的两部分合二为一。如果存储了用户喜欢的数字，就显示它，否则提示用户输入喜欢的数字并将其存储到文件中。运行该程序两次，看是否像预期的那样工作。

import json

filename = 'favorite number.json'
try:
    with open(filename) as f_obj:
        number = json.load(f_obj)
    print("I know your favorite number! It's " + number + ".")
except FileNotFoundError:
    favorite_num = input("Enter your favorite number: ")
    with open(filename, 'w') as f_obj:
        json.dump(favorite_num, f_obj)

10-13 验证用户：最后一个remember_me.py版本，假设用户要么已经输入其用户名，要么是首次运行该程序。应修改这个程序，以应对这样的情形：当前和最后一次运行该程序的用户并非同一个人。

　　为此，在greet_user()中打印欢迎用户回来的消息，先询问他用户名是否是对的。如果不对，就调用get_new_username()让户输入正确的用户名。

import json


def get_stored_username():
    """如果存储了用户名，就获取它"""
    filename = 'username.json'
    try:
        with open(filename) as f_obj:
            username = json.load(f_obj)
    except FileNotFoundError:
        return None
    else:
        return username


def get_new_username():
    """提示用户输入用户名"""
    username = input('What is your name? ')
    filename = "username.json"
    with open(filename, 'w') as f_obj:
        json.dump(username, f_obj)
    return username


def greet_user():
    """判断当前用户是否对，问候用户或存储新用户"""
    username = get_stored_username()
    message = "Does the " + username + " is your username? Enter yes or no: "
    yes_or_no = input(message)
    if yes_or_no == 'yes':
        print("Welcome back, " + username + "!")
    else:
        username = get_new_username()
        print("We'll remember you when you come back, " + username + "!")


greet_user()