string类型

say = "hello world"
print(say[-1])   #  d
print(say[-5:])   # > world
print(say[:5])   # >hello
print(say[i:j:k])  #  i=开始位置，J= 结束位置  k=跳数

say = "there is 3 monkey in the tree!"   # 3 和 tree 不确定是：
say = "there is %d monkey in the %s!"
print(say % (3,"water"))    
 

ip = 192.168.2.123
ipNew = ip.split('.')   # ipNew = ['192', '168', '1', '123']
".".join(ipNew)    #"192.168.1.123"
"__".join(ipNew)    #192__168__1__123"