old_contents: import serial
  import time
  import random
  
  ser = serial.Serial('COM14', 250000, timeout=1)
  print "Initializing emulator..."
  
  """Add response callbacks here"""
  def randomTemp(command):
  	# temp commands look like this: ok T:19.4 /0.0 B:0.0 /0.0 @:0 B@:0
  	return "ok T:%s\n" % random.randrange(202,215)
  
  def echo(command):
  	return command
  
  """Dictionary of command and response callback"""
  responses = { "M105" : randomTemp, "A": echo}
  
  def getCorrectResponse(command):
  	try:
  		#Remove line returns
  		command = ''.join(command.splitlines())
  		if command in responses:			
  			return responses[command](command)
  	except Exception, e:
  		print e
  		
  	return 'ok\n'
  
  while True:
  	line = ser.readline()   # read a '\n' terminated line
  	if len(line) > 0:
  		print(line)
  		response = getCorrectResponse(line)
  		print response
  		ser.write(response)
  ser.close()
new_contents: # Copyright (c) 2015, Lars Brubaker
  # All rights reserved.
  # 
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions are met: 
  # 
  # 1. Redistributions of source code must retain the above copyright notice, this
  #    list of conditions and the following disclaimer. 
  # 2. Redistributions in binary form must reproduce the above copyright notice,
  #    this list of conditions and the following disclaimer in the documentation
  #    and/or other materials provided with the distribution. 
  # 
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  # WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  # DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
  # ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  # (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  # LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  # ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  # 
  # The views and conclusions contained in the software and documentation are those
  # of the authors and should not be interpreted as representing official policies, 
  # either expressed or implied, of the FreeBSD Project.
  
  # This is to test connection and printing. We use it with com0com 
  # to validate MatterControl under various situations.
  import sys
  import argparse
  import serial
  import time
  import random
  
  """Add response callbacks here"""
  def randomTemp(command):
  	# temp commands look like this: ok T:19.4 /0.0 B:0.0 /0.0 @:0 B@:0
  	return "ok T:%s\n" % random.randrange(202,215)
  
  def echo(command):
  	return command
  
  def getCorrectResponse(command):
  	try:
  		#Remove line returns
  		command = ''.join(command.splitlines())
  		if command in responses:			
  			return responses[command](command)
  	except Exception, e:
  		print e
  		
  	return 'ok\n'
  
  """Dictionary of command and response callback"""
  responses = { "M105" : randomTemp, "A": echo}
  
  def main(argv):
  	parser = argparse.ArgumentParser(description='Set up a printer emulation.')
  	ser = serial.Serial('COM14', 250000, timeout=1)
  	waitForKey = True
  	print "Initializing emulator..."
  	while True:
  		line = ser.readline()   # read a '\n' terminated line
  		if len(line) > 0:
  			print(line)
  			response = getCorrectResponse(line)
  			print response
  			ser.write(response)
  	ser.close()
  
  if __name__ == "__main__":
  	main(sys.argv[1:])
  
subject: Put in a main and a start an argparse for command line args.