capitallize首字母大写
>>> str1.capitalize()
'I love china'
casefold所有字母小写
>>> str2 = "ADASF"
>>> str2.casefold()
'adasf'
center(width)字符串居中并填充空格到指定长度
>>> str2.center(20)
' ADASF '
count(sub[,start[,end]])元素出现的次数
>>> str1 = "agdssdggssa"
>>> str1.count("s")
4
endswith(sub[,start[,end]])检查是不是以sub结束
>>> str1 = "agdssdggssa"
>>> str1.endswith("sa")
True
extendtabs(tablesize=8)把\t替换成空格
>>> str1 = "asdf\taf\tsa\tesf"
>>> str1.expandtabs(tabsize=3)
'asdf af sa esf'
find（）找到元素的索引值
>>> str1 = "agdssdggssa"
>>> str1.find("a")
0
>>> str1.find("w")
-1
参考小甲鱼老师
https://fishc.com.cn/forum.php?mod=viewthread&tid=38992&extra=page%3D1%26filter%3Dtypeid%26typeid%3D403
