Python non-blocking execute every x seconds.Used on my raspberry pi to update the display on my (Adafruit LCD+Keypad)[http://www.adafruit.com/products/1115] board while still being able to constantly poll for button presses.Also updates the display with current date+time and wifi IP address.

ipplate.py

#!/usr/bin/python

from sys import exit

from Adafruit_CharLCDPlate import Adafruit_CharLCDPlate
from subprocess import * 
from time import sleep, strftime
from datetime import datetime
import time

# Define global vars
lcd = Adafruit_CharLCDPlate()
cmd = "ip addr show wlan0 | grep inet | awk '{print $2}' | cut -d/ -f1"

# Define fn's
def update_display(): 
   lcd.home()
	ipaddr = run_cmd(cmd)
	lcd.message(datetime.now().strftime('%b %d  %H:%M:%S\n'))
	lcd.message('IP %s' % ( ipaddr ) )

def run_cmd(cmd):
        p = Popen(cmd, shell=True, stdout=PIPE)
        output = p.communicate()[0]
        return output


# Startup
lcd.clear()
millis = int(round(time.time() * 1000))
lastMillis = millis

# Loop
while 1:
	millis = int(round(time.time() * 1000))
	
	if millis - lastMillis >= 1000:
		update_display()
		lastMillis = millis

	if lcd.buttonPressed(lcd.SELECT):
		lcd.clear()
		lcd.backlight(lcd.OFF)
		exit(0)