old_contents: #!/usr/bin/env python
  
  from argparse import ArgumentParser
  import sys
  import serial
  
  def run(device, baud):
      with serial.Serial(device, baud, timeout=0.1) as ser:
          while True:
              line = ser.readline()
              if line:
                  sys.stdout.write(line)
  
  if __name__ == '__main__':
      parser = ArgumentParser()
      parser.add_argument('device',
                          help='serial device, typically /dev/tty.usbserial-*')
      parser.add_argument('--baud', dest='baud', type=int, default=74880)
      args = parser.parse_args()
      run(args.device, args.baud)
  
new_contents: #!/usr/bin/env python
  
  from argparse import ArgumentParser
  import sys
  import serial
  from datetime import datetime
  
  def run(device, baud, prefix=None):
      with serial.Serial(device, baud, timeout=0.1) as ser:
          while True:
              line = ser.readline()
              if not line:
                  continue
              if prefix:
                  line = prefix() + line
              sys.stdout.write(line)
  
  if __name__ == '__main__':
      parser = ArgumentParser()
      parser.add_argument('device',
                          help='serial device, typically /dev/tty.usbserial-*')
      parser.add_argument('--baud', dest='baud', type=int, default=74880)
      parser.add_argument('-t', '--timestamp', dest='timestamp', action='store_true',
                          help="Add timestamp to start of each line")
      args = parser.parse_args()
      prefix = None
      if args.timestamp:
          prefix = lambda: datetime.now().strftime("[%H:%M:%S.%f] ")
      run(args.device, args.baud, prefix)
  
subject: Add option to timestamp each line from serial