一、字符串连接

s1 = 'hello'
s2 = 'world'
s3 = s1 + ' ' +s2
print(s3)   #print:   hello world

二、字符串反转

s1 = 'hello world'
s2 = s1[::-1]
print(s2)   #print:   dlrow olleh

三、字符串长度

s1 = 'hello world'
ret = len(s1)
print(ret)   #print:  11

四、字符串包含

s1 = 'hello world'
ret = 'h' in s1
print(ret)   #print:  true

 五、字符串索引

s = 'fheiogfj'
print(s[2]) #print: e
print(s[:2])    #print: fh
print(s[4:])    #print:ogfj