Better Python Tea Timer

#!/Users/jgraves/environments/python/bin/python

import time
import sys
import Growl

try:
    minutes = float(sys.argv[1])
except IndexError:
    print "How many minutes?"
    sys.exit()

time.sleep(60 * minutes)

notifier = Growl.GrowlNotifier('Tea Timer', ['ntf1'])
notifier.register()
notifier.notify('ntf1', 'Tea Timer', 'It\'s tea time!')