字符串的基础操作:
1、str1 + str2
将字符串连接
s1="abc" s2="123" print(s1+s2) abc123
2、str * num
s1="abc" print(s1*3) abcabcabc
3、str[index]
s1="abc" print(s1[0]) a
4、str[index:index:step]
s1="abcdef" print(s1[2::2]) ce
Mark on 2018.4.6