human
Solve in Python:
Given a string and an integer k, you need to reverse the first k characters for every 2k characters counting from the start of the string. If there are less than k characters left, reverse all of them. If there are less than 2k but greater than or equal to k characters, then reverse the first k characters and left the other as original.

Example:

Input: s = "abcdefg", k = 2
Output: "bacdfeg"


Restrictions: 

 The string consists of lower English letters only.
 Length of the given string and k will in the range [1, 10000]
assistant
#Here is the Python program you requested.

class Solution:
     def reverseStr(self, s, k):
         """
         :type s: str
         :type k: int
         :rtype: str
         """
         
         i = 0
         tmp = 0
         ret = ""
         while i < len(s):
             if len(s)-i < k:
                 tmp = len(s)-i
             else:
                 tmp = k
             ttmp = tmp    
             while ttmp!= 0:
                 ret += s[i+ttmp-1]
                 ttmp -= 1
             
             i+=tmp
             if len(s)-i < k:
                 tmp = len(s)-i
             else:
                 tmp = k
             ttmp = tmp
             
             while ttmp!= 0:
                 ret += s[i]
                 i+=1
                 ttmp -= 1
 
         return ret