练习 10-11 喜欢的数

编写一个程序，提示用户输入喜欢的数，并使用 json.dump() 将这个数存储到文件中。再编写一个程序，从文件中读取这个值，并打印如下所示的消息。

I know your favorite number！It's _________.

1 import json
2 
3 filename = 'number.json'
4 
5 with open(filename, 'w') as f:
6     number = input("Please enter your favorite number: ")
7     number = int(number)
8     json.dump(number, f)

1 import json
2 
3 filename = 'number.json'
4 
5 with open(filename) as f:
6     number = json.load(f)
7     print(f"I know your favorite number! It's {number}")

练习 10-12 记住喜欢的数

将练习10-11中的程序合二为一。如果存储了用户喜欢的数，就像用户显示它，否则提示用户输入喜欢的数并将其存储到文件中。运行这个程序两次，看看它能否像预期的那样工作。

 1 import json
 2 
 3 filename = 'favorite_number.json'
 4 
 5 try:
 6     with open(filename) as f:
 7         number = json.load(f)
 8 except FileNotFoundError:
 9     with open(filename, 'w') as f:
10         number = input("Please enter your favorite number: ")
11         number = int(number)
12         json.dump(number, f)
13         print("We will remeber your favorite number.")
14 else:
15     print(f"I know your favorite number. It's {number}")