If snmpget is not in your paths I don't think just calling it like that would work but instead you would need the full path like C:\Some\Path\bin\snmpget. But I don't know that that is your issue here. Regardless I would suggest trying to use ProcessBuilder instead to get data out of calling a process, it seems to work a bit better - Procedure for installing python libraries from source - #16 by PGriffith
How does it go if you use the full path?