control ubuntu audio volume from python

vol-ctrl.py

from subprocess import call
from time import sleep
from datetime import datetime
import argparse

if __name__ == '__main__' :
    parser = argparse.ArgumentParser(progname='python vol-ctrl.py', description='decrease volume with delay')
    parser.add_argument('-i','--init',type=int,help='initial volume')
    parser.add_argument('-r','--rate',type=int,help='decrease rate')
    parser.add_argument('-d','--delay',type=int,help='decrease delay in seconds')
    args = parser.parse_args()
    volume = 35
    decrease_rate = 5
    decrease_delay = 10 #seconds
    if args.init :
        volume = args.init
    if args.rate :
        decrease_rate = args.rate
    if args.delay :
        decrease_delay = args.delay
    cmd = ['pactl','set-sink-volume','@DEFAULT_SINK@','%s%%'%volume]
    while volume > 0 :
        vol = volume
        for i in range(decrease_rate) :
            vol = vol - 1 
            cmd[-1] = '%s%%'%vol
            call(cmd)
            print(datetime.now().strftime("%Y-%m-%d %H:%M") + ' volume : '+cmd[-1])
            sleep(1)
        volume = vol
        sleep(decrease_delay)