字符串格式化输出用于字典的两种不同方式

　　format()方法：

>>> stu
{'name': 'Jack', 'sex': 'm', 'age': 22}
>>> 'his name is {name}, his age is {age}'.format(**stu)
'his name is Jack, his age is 22'

　　format_map()方法：

>>> 'his name is {name}, his age is {age}'.format_map(stu)
'his name is Jack, his age is 22'