Python往字符串里塞一个‘-’的小程序

    想实现这样一个程序：任意输入一个字符串，要求在字母与数字的衔接处加一个‘-’，比如：输入FO123,等到得到FO-123,如果输入FO-123，输出的还是FO-123,如果不是字母和数字衔接组合，则原样输出，比如FO~123,或者FOFO，或者1234，或者~WER12，都是原样输出。

 

程序原码是这样：

 

import string

s = input("please input astring:")

leng = len(s)

index = 0

for key in s:

    index=index+1

    if key in string.ascii_letters:  # string.ascii_letters是所有大小写字a-z,A-Z字符

         continue

    elif key in string.digits:

         if index == 1:       #第一个字符不可以是数字，如果是数字，就跳出

              break

         s = s[:index-1]+'-'+s[index-1:] #重新组合，之后跳出

         break

    else:

         break            #第一个字符不是字母不是数字，直接跳出

         

print(s)    

 

下面是程序运行效果：

Python 3.5.0 (v3.5.0:374f501f4567, Sep 13 2015, 02:27:37) [MSC v.1900 64 bit (AMD64)] on win32
Type "copyright", "credits" or "license()" for more information.
>>>
================== RESTART: C:\Users\jiess\Documents\kk.py ==================
please input a string:FO123
FO-123
>>>
================== RESTART: C:\Users\jiess\Documents\kk.py ==================
please input a string:FO-123
FO-123
>>>
================== RESTART: C:\Users\jiess\Documents\kk.py ==================
please input a string:fo~123
fo~123
>>>
================== RESTART: C:\Users\jiess\Documents\kk.py ==================
please input a string:1234
1234
>>>
================== RESTART: C:\Users\jiess\Documents\kk.py ==================
please input a string:~FOFO
~FOFO
>>>