str.capitalize 首字符大写

字符串方法 str.capitalize()，Python 官方文档描述如下：

help(str.capitalize)

Help on method_descriptor:

capitalize(self, /)
    Return a capitalized version of the string.
    
    More specifically, make the first character have upper case and the rest lower
    case.

返回原字符串的副本，其首个字符大写，其余为小写:

'pyTHON'.capitalize()

'Python'

只有首个字符是字母，才会将首个字符大写：

'嗨 pyTHON'.capitalize()

'嗨 python'