old_contents: from __future__ import absolute_import
  from __future__ import print_function
  from __future__ import division
  
  
  def sum_list_for(num_ls):
      """Sum number list by for loop."""
      _sum = 0
      for num in num_ls:
          _sum += num
      return _sum
  
  
  def sum_list_recur(num_ls):
      """Sum number list by recursion."""
      if len(num_ls) == 1:
          return num_ls[0]
      else:
          return num_ls[0] + sum_list_recur(num_ls[1:])
  
  
  def main():
      import time
  
      num_ls = [0, 1, 2, 3, 4, 5]
      
      start_time = time.time()
      print('By for loop: {}'.format(sum_list_for(num_ls)))
      print('Time: {}'.format(time.time() - start_time))
  
      start_time = time.time()
      print('By recursion: {}'.format(sum_list_recur(num_ls)))
      print('Time: {}'.format(time.time() - start_time))
  
  
  if __name__ == '__main__':
      main()
  
new_contents: from __future__ import absolute_import
  from __future__ import print_function
  from __future__ import division
  
  
  def sum_list_iter(num_ls):
      """Sum number list by for loop."""
      _sum = 0
      for num in num_ls:
          _sum += num
      return _sum
  
  
  def sum_list_recur(num_ls):
      """Sum number list by recursion."""
      if len(num_ls) == 1:
          return num_ls[0]
      else:
          return num_ls[0] + sum_list_recur(num_ls[1:])
  
  
  def main():
      import time
  
      num_ls = range(100)
      
      start_time = time.time()
      print('By iteration: {}'.format(sum_list_iter(num_ls)))
      print('Time: {}'.format(time.time() - start_time))
  
      start_time = time.time()
      print('By recursion: {}'.format(sum_list_recur(num_ls)))
      print('Time: {}'.format(time.time() - start_time))
  
  
  if __name__ == '__main__':
      main()
  
subject: Rename to sum_list_iter() and revise main()'s num_ls