连续最长字符串

1、不区分大小写
2、返回连续最长串的长度
3、拷贝给新串

例如：输入123abcdefg2141as324
返回最长字串为abcdefg
字串长度为7

#! /usr/bin/python

def test_1(a):
   a=a.lower()
   result=[]
   all_words="abcdefghijklmnopqrstuvwxyz"
   re=[]       
   for i in range(1,len(a)+1):
       str_list=[]
       result={}
       for j in range(0,i):
           if a[j:len(a)-i+j+1] in all_words:  
               str_list.append(a[j:len(a)-i+j+1])
               result[len(a)-i+1]=list(set(str_list))
           else:
               pass
       re.append(result)
   for i in re:
       if  i:
           for k,v in i.items():
               return  k,v

if __name__=="__main__":
   a='aabAhijkvWxysasz'
   print(test_1(a))