541. Reverse String II

class Solution:
    def reverseStr(self, s, k):
        """
        :type s: str
        :type k: int
        :rtype: str
        """
        new_list = list(s)
        i = 0
        while i< len(s):
            if i+k > len(s):
                new_list[i:] = new_list[i:][::-1]
            else:
                new_list[i:i+k] = new_list[i:i+k][::-1]
            i = i+k*2
        return ''.join(new_list)