简单字符串过滤练习

 1 # -*- coding:utf-8 -*-

 2 

 3 import string

 4 

 5 alphas = string.letters + '_'            #返回26个大小写字母

 6 nums = string.digits                    #返回字符串 0,1,2,3,4,5,6,7,8,9

 7 #print alphas

 8 #print nums

 9 print 'Welcome to the Identifier Checker v1.0'

10 print 'Testees must be at least 2 chars long.'

11 

12 myInput = raw_input('Identifier to test?')

13 

14 if len(myInput) > 1:                    #过滤长度小于2的字符串

15     if myInput[0] not in alphas:        #检查第一个字符串是不是字母或下划线，如果不是，输出结果并退出

16         print 'invalid: first symbol must bealphabetic'

17     else:

18         for otherChar in myInput[1:]:               #循环字符串 myInput 从索引位置1开始

19             if otherChar not in alphas + nums:      #检查字符串，如果包括非 alphas 中的字符, 打印输出

20                 print otherChar                     #输出非法字符

21                 print myInput.find(otherChar)       #输出第一个非法字符的索引

22                 print 'invalid: remainig symbols must be alphanumeric'

23                 break

24 else:

25     print 'okay as an identifier'