old_contents: """Read and print an integer series."""
  
  import sys
  
  
  def read_series(filename):
      f = open(filename, mode='rt', encoding='utf-8')
      series = []
      for line in f:
          a = int(line.strip())
          series.append(a)
      f.close()
      return series
  
  
  def main(filename):
      print(read_series(filename))
  
  
  if __name__ == '__main__':
      main(sys.argv[1])
  
new_contents: """Read and print an integer series."""
  
  import sys
  
  
  def read_series(filename):
      try:
          f = open(filename, mode='rt', encoding='utf-8')
          return [int(line.strip()) for line in f]
      finally:
          f.close()
  
  
  def main(filename):
      print(read_series(filename))
  
  
  if __name__ == '__main__':
      main(sys.argv[1])
  
subject: Refactor to ensure closing and also use list comprehension