new_contents: # recursive binary search
  # return, if present, the position of the searched element
  # returns -1 if the element is not present
  
  def recursive_binary_search(n, e, i, j):
      if i > j:
          return -1
  
      half = (i+j)/2
  
      if e == n[half]:
         return half
  
      elif e < n[half]:
         return binary_search(n, e, i, half-1)
  
      elif e > n[half]:
         return binary_search(n, e, half+1, j)
  
  
  def test():
      a_list = [1,5,7,8,13,17,21,27,33,37,40]
      item = 21
      start = 0
      end = len(a_list)-1
      assert recursive_binary_search(a_list, item, start, end) == 6
  
  if __name__ == "__main__":
      test()
  
subject: Add recursive binary search in python