How to differentiate VM is loaded/installed with OS or not using command

Hi,
My requirement is to check whether VM is loaded/installed with OS are not using command line (i.e. python script).

"vdsClient -s 0 getAllVmStats | grep Status"

command is showing "UP" even if it not installed OS. SO how to differentiate VM is having OS or not.

and also I want command to check list of all VM's (i.e. both running and shutdown).

Please help us!!!