Python controlador musica

Python

import serial
import os

def U():
    print 'boton Up volumen++'
    os.system("amixer sset Master playback 5%+")
def D():
    print 'boton Down volmen--'
    os.system("amixer sset Master playback 5%-")
def L():
    print 'boton L restart'
    os.system("banshee --restart-or-previous")
def R():
    print 'boton R next song'
    os.system("banshee --next")
def A():
    print 'boton A toogle playing'
    os.system("banshee --toggle-playing")
def S():
    print 'boton Start inicia banshee'
    os.system("banshee &")
def C():
    print 'Boton select termina banshee'
    os.system("killall banshee")
def B():
    print 'boton B stop'
    os.system("banshee --stop")
def N():
    print 'Nada'
    
def run(program, *args):
    pid = os.fork()
    if not pid:
        os.execvp(program, (program,) +  args)
    return os.wait()[0]

s = serial.Serial("/dev/ttyACM"+raw_input("En que puerto serial esta el arduino: "),9600)

while(1):
    case = {
        'U' : U,
        'D' : D,
        'R' : R,
        'L' : L,
        'S' : S,
        'A' : A,
        'B' : B,
        'N' : N,
        'C' : C,
        }
    case[s.read()]()