Modify the case of the string title(), upper(), lower()

title()： Capitalize the first letter of each word , The space between words can be used 、 Slashes, etc .

upper()： Make every letter capitalized .

lower()： Make each letter lowercase .

>>> s='wo shi xiaoguaishou'
>>> s.title()
'Wo Shi Xiaoguaishou'
>>> sss='wo\shi\ xiaoguaoshou'
>>> sss.title()
'Wo\\Shi\\ Xiaoguaoshou'

>>> ss=s.upper()
>>> ss
'WO SHI XIAOGUAISHOU'

>>> ss.lower()
'wo shi xiaoguaishou'