Buttons Ver 1.0

import RPi.GPIO as GPIO
import time
import os
import subprocess

GPIO.setwarnings(False)
GPIO.setmode(GPIO.BOARD)
GPIO.setup(3,GPIO.IN)
GPIO.setup(5,GPIO.IN)
GPIO.setup(7,GPIO.IN)
GPIO.setup(19,GPIO.IN)
GPIO.setup(21,GPIO.IN)
GPIO.setup(23,GPIO.IN)
devnull = open(os.devnull, 'wb')

prev_input_stop = 1
prev_input_ff = 1
prev_input_rw = 1
counter_stop = 0
counter_ff = 0
counter_rw = 0

def shutdown():
  command = "sudo shutdown -h now"
  process = subprocess.Popen(command.split(), stdout=subprocess.PIPE)
  output = process.communicate()[0]
  print output


def stop():
  command = "mpc -q stop"
  process = subprocess.Popen(command.split(), stdout=devnull, shell=False)
  output = process.communicate()[0]
  #print output

def toggle():
  command = "mpc -q toggle"
  process = subprocess.Popen(command.split(), stdout=devnull, shell=False)
  output = process.communicate()[0]
  #print output

def vol_up():
  command = "mpc -q volume +10"
  process = subprocess.Popen(command.split(), stdout=devnull, shell=False)
  output = process.communicate()[0]
  #print output

def vol_down():
  command = "mpc -q volume -10"
  process = subprocess.Popen(command.split(), stdout=devnull, shell=False)
  output = process.communicate()[0]
  #print output

def next():
  command = "mpc -q next"
  process = subprocess.Popen(command.split(), stdout=devnull, shell=False)
  output = process.communicate()[0]
  #print output

def prev():
  command = "mpc -q prev"
  process = subprocess.Popen(command.split(), stdout=devnull, shell=False)
  output = process.communicate()[0]
  #print output


while True:
#Read switches
  play_btn = GPIO.input(7)
  ff_btn = GPIO.input(21)
  rw_btn = GPIO.input(19)
  stop_btn = GPIO.input(23)
####STOP/POWER BUTTON
#If a button is pressed and the previous state was not before then do primary action
  if ((not play_btn) and (prev_input_play)):
    toggle()
  if ((not stop_btn) and (prev_input_stop)):
    stop()
  if ((not ff_btn) and (prev_input_ff)):
    vol_up()
  if ((not rw_btn) and (prev_input_rw)):
    vol_down()
#If a button is pressed and continues to be pressed then add 1 to appropriate counter
  if ((not stop_btn) and (not prev_input_stop)):
    counter_stop = counter_stop + 1
  if ((not ff_btn) and (not prev_input_ff)):
    counter_ff = counter_ff + 1
  if ((not rw_btn) and (not prev_input_rw)):
    counter_rw = counter_rw + 1
#Update buttons previous states
  prev_input_stop = stop_btn
  prev_input_ff = ff_btn
  prev_input_rw = rw_btn
  prev_input_play = play_btn
#If any buttons have been released then reset counter to zero
  if (stop_btn):
    counter_stop = 0
  if (ff_btn):
    counter_ff = 0
  if (rw_btn):
    counter_rw = 0
#If any button is held 2 seconds then run secondary function for that button
#Power down function requires a longer press
  if (counter_stop == 24):
    shutdown()
  if (counter_ff == 8):
    next()
  if (counter_rw == 8):
    prev()
  time.sleep(0.1)