btnAndLed.py

#!/usr/bin/env python

#-----------------------------------------------------------
# File name   : 05_btnAndLed_1.py
# Description : toggle an LED by button.
# Author      : Jason
# E-mail      : jason@adeept.com
# Website     : www.adeept.com
# Date        : 2015/06/12
#-----------------------------------------------------------

import RPi.GPIO as GPIO

LedPin = 11    # pin11 --- led
BtnPin = 12    # pin12 --- button

def setup():
        GPIO.setmode(GPIO.BOARD)       # Numbers GPIOs by physical location
        GPIO.setup(LedPin, GPIO.OUT)   # Set LedPin's mode is output
        GPIO.setup(BtnPin, GPIO.IN, pull_up_down=GPIO.PUD_UP)    # Set BtnPin's mode is input, and pull up to high level(3.3V)
        GPIO.output(LedPin, GPIO.HIGH) # Set LedPin high(+3.3V) to make led off

def loop():
    while True:
        if GPIO.input(BtnPin) == GPIO.LOW: # Check whether the button is pressed or not.
            print '...led on'
            GPIO.output(LedPin, GPIO.LOW)  # led on
        else:
            print 'led off...'
            GPIO.output(LedPin, GPIO.HIGH) # led off

def destroy():
    GPIO.output(LedPin, GPIO.HIGH)     # led off
    GPIO.cleanup()                     # Release resource

if __name__ == '__main__':     # Program start from here
    setup()
    try:
        loop()
    except KeyboardInterrupt:  # When 'Ctrl+C' is pressed, the child program destroy() will be  executed.
        print '\n***Resources released & destroyed***'
        destroy()