I work with python 2.7.8 and i use this code to close all open applications:
import os,subprocess
os.system('taskkill /im chrome.exe')
os.system('taskkill /im POWERPNT.exe')
os.system('taskkill /im OUTLOOK.exe')
os.system('taskkill /im WINWORD.exe')
os.system('taskkill /im ArcMap.exe')
os.system('taskkill /im acadlt.exe')
os.system('taskkill /im EXCEL.exe')
os.system('taskkill /im AcroBat.exe')
os.system('taskkill /im wmplayer.exe')
subprocess.call('nircmd.exe win close class "CabinetWClass"' , shell=True)
I succeed to close all applications except OUTLOOK and all the open folder of the windows 7 Professional