from AppKit import NSWorkspace
import time
from datetime import datetime

date = str(datetime.now().date())
apptimes = {}

try:
    while True:
        app = NSWorkspace.sharedWorkspace().activeApplication()['NSApplicationName']
        apptimes[app] = apptimes.get(app, 0) + 1
        time.sleep(1)
finally:
    filename = date + ".txt"
    f = open("/Users/me/Library/AppTimes/" + filename, 'w+')
    f.write(str(apptimes))
    f.close()