turn on on tv with cec

[rana]

i tried making a addon so i can call the addon to run the script to turn off the tv didnt have any luck anyone want to look at and let me know what im doing wrong

here is the addon.xml file

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<addon id="service.script.tvoff" name="Tv off" version="0.1.0" provider-name="RaNa">
<requires>
<import addon="xbmc.python" version="2.1.0"/>
</requires>
<extension point="xbmc.python.pluginsource" library="off.py">
<provides>executable</provides>
</extension>
<extension point="xbmc.addon.metadata">
</extension>
</addon>

and here is the off.py

import os
os.system('echo "standby 0" | cec-client -s')

not sure why its not working