Python 2 class for blinking the onboard ACT LED on the Raspberry PI 3

rpi3led.py

#/usr/bin/python -p
import time
import subprocess
import threading

"""
This is a class for blinking the onboard ACT LED on the Raspberry PI 3 based on 
shell commands. There should be a way to do this via GPIO, but for me it did not
work so far. Here are some relevant links for blinking via GPIO:
* https://kofler.info/on-board-leds-des-raspberry-pi-steuern/
* https://www.raspberrypi.org/forums/viewtopic.php?f=44&t=144787


Example:

import time
l = LED()

# turn on LED
l.led(True)

# turn off LED
l.led(False)

# turn on LED and then turn it off after 1 second
l.led(True, 1)

# some blinking patterns

l.start()
time.sleep(5)
l.stop()

l.start_simple(3,0.1,1)
time.sleep(5)
l.stop()

l.start_offset(3,0.1,0.2,1)
time.sleep(5)
l.stop()

l.start_simple([0.1,0.1,0.1,0.25,1])
time.sleep(5)
l.stop()


Credits:

* https://stackoverflow.com/questions/18018033/how-to-stop-a-looping-thread-in-python
* https://kofler.info/on-board-leds-des-raspberry-pi-steuern/
"""
class LED:

    def __init__(self):
        subprocess.call("echo \"none\" > /sys/class/leds/led0/trigger", shell=True)

    def start_loop(self, loop_body):
        def run():
            while not self.stop_event.is_set():
                loop_body()

        self.stop_event = threading.Event()
        thread = threading.Thread(target=run)
        thread.start()
        return self

    def start(self):
        self.start_loop(lambda: self.blink_offset(1, 1, 1, 1))

    def start_simple(self, blinks, quick, slow):
        self.start_loop(lambda: self.blink_offset(blinks, quick, quick, slow))

    def start_offset(self, blinks, on, off, out):
        self.start_loop(lambda: self.blink_offset(blinks, on, off, out))

    def start_generic(self, onoff):
        self.start_loop(lambda: self.blink_generic(onoff))

    def led(self, on, reset = -1):
        if on:
            subprocess.call("echo 1 > /sys/class/leds/led0/brightness", shell=True)
        else:
            subprocess.call("echo 0 > /sys/class/leds/led0/brightness", shell=True)
        if reset > 0:
            time.sleep(reset)
            self.led(not on)

    def blink_offset(self, blinks, on, off, out):
        time.sleep(out)
        for i in range(blinks):
            self.led(True, on)
            time.sleep(off)

    def blink_generic(self, onoff):
        for i in range(len(onoff) / 2):
            on = onoff[i * 2]
            off = onoff[i * 2 + 1]
            self.led(True, on)
            time.sleep(off)
            
    def stop(self):
        self.stop_event.set()