使用 input() 函数输入一个人的姓名、年龄和手机号码，再分别使用 %格式符和 format 格式符输出: 姓名:....，年龄: ....，手机号码: ...... 。

Null is a term used in computer programming and database management to represent the absence of a value or a lack of information. It is typically used to indicate that a particular variable, field, or record does not contain any data or has not yet been assigned a value. The value of null is often used as a placeholder or default value in programming languages and databases.