Given a string S, return the "reversed" string where all characters that are not a letter stay in the same place, and all letters reverse their positions.

Example 1:

Input: "ab-cd"
Output: "dc-ba"

Example 2:

Input: "a-bC-dEf-ghIj"
Output: "j-Ih-gfE-dCba"

Example 3:

Input: 
 
"Test1ng-Leet=code-Q!"
Output: "Qedo1ct-eeLg=ntse-T!"

Note:

1. S.length <= 100
2. 33 <= S[i].ASCIIcode <= 122 
3. S doesn't contain \ or "

class Solution:
    def reverseOnlyLetters(self, S):
        """
        :type S: str
        :rtype: str
        """
        #S="a-bC-dEf-ghIj"
        revStr="".join([c for c in reversed(S) if c.isalpha()])
        
        for k,v in enumerate(S):
            if not v.isalpha():
                revStr=revStr[:k]+v+revStr[k:]
        return revStr
 

isalpha(): 返回布林值

http://www.runoob.com/python3/python3-string-isalpha.html

reversed()

http://www.runoob.com/python3/python3-func-reversed.html