gistfile1.py

import serial                                                                   
import xml.etree.ElementTree as ET                                              
import os                                                                       
                                                                                
port = '/dev/ttyUSB0'                                                           
baud = 57600                                                                    
ser = serial.Serial(port, baud)                                                 
                                                                                
data = ser.readline()                                                           
root = ET.fromstring(data)                                                      
                                                                                
watts = root[7][0].text                                                         
temp  = root[3].text                                                            
                                                                                
rrdpath = '/etc/cron.cc/rrd/powertemp.rrd'                                      
rrdcmd = '/usr/bin/rrdtool update %s N:%s:%s' % (rrdpath, watts, temp)          
os.system(rrdcmd)