old_contents: def selection_sort(a_list):
      """Selection Sort algortihm.
  
      Concept: Find out the maximun item's original slot first,
      then switch it to the max slot. Iterate the procedure.
      """
      for max_slot in reversed(range(len(a_list))):
          select_slot = 0
          for slot in range(1, max_slot + 1):
              if a_list[slot] > a_list[select_slot]:
                  select_slot = slot
  
          temp = a_list[max_slot]
          a_list[max_slot] = a_list[select_slot]
          a_list[select_slot] = temp
  
  
  def main():
      a_list = [54, 26, 93, 17, 77, 31, 44, 55, 20]
      print('a_list: {}'.format(a_list))
      print('By selection sort: ')
      selection_sort(a_list)
      print(a_list)
  
  
  if __name__ == '__main__':
      main()
  
new_contents: def selection_sort(a_list):
      """Selection Sort algortihm.
  
      Concept: 
        - Find out the maximun item's original slot first,
        - then swap it and the item at the max slot. 
        - Iterate the procedure.
      """
      for max_slot in reversed(range(len(a_list))):
          select_slot = 0
          for slot in range(1, max_slot + 1):
              if a_list[slot] > a_list[select_slot]:
                  select_slot = slot
  
          temp = a_list[max_slot]
          a_list[max_slot] = a_list[select_slot]
          a_list[select_slot] = temp
  
  
  def main():
      a_list = [54, 26, 93, 17, 77, 31, 44, 55, 20]
      print('a_list: {}'.format(a_list))
      print('By selection sort: ')
      selection_sort(a_list)
      print(a_list)
  
  
  if __name__ == '__main__':
      main()
  
subject: Revise doc string for selection sort’s concept