Raspberry Pi LED for new emails

Question

I'm learning how to use Python with the Raspberry Pi. I successfully followed the tutorial for how to have a Python script run on the Pi to check for new email and turn on an LED if any new messages are in an inbox. I wanted to give myself a challenge by adding a feature to blink a secondary LED to indicate the number of waiting messages. I played around for a while and got a script working, but would like to know if I implemented this correctly.

Am I using threading correctly? Is there an easier way to check a feed every n seconds, and if new messages are present, then continually run blink() until the next feed check?

#!/user/bin/env python
from threading import Thread, Event
from time import sleep
import feedparser
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
BLUE_LED = 17
BIG_LED = 23
GPIO.setup(BLUE_LED, GPIO.OUT)
GPIO.setup(BIG_LED, GPIO.OUT)
USERNAME = "[email protected]"
PASSWORD = "gzvioCNiAvFvKoqY"
class Repeat(Thread):
 def __init__(self,delay,function,*args,**kwargs):
 Thread.__init__(self)
 self.abort = Event()
 self.delay = delay
 self.args = args
 self.kwargs = kwargs
 self.function = function
 def stop(self):
 self.abort.set()
 def run(self):
 while not self.abort.isSet():
 self.function(*self.args,**self.kwargs)
 self.abort.wait(self.delay)
def blink(count):
 for x in range(0, count):
 print "blink", x + 1
 GPIO.output(BLUE_LED, True)
 sleep(.25)
 GPIO.output(BLUE_LED, False)
 sleep(.25)
 sleep(1) #pause between blinks
try:
 while True:
 print "Starting b"
 b = Repeat(1,blink,0)
 b.start()
 big_led = 0
 print "---> ---> Checking feed"
 messages = int(feedparser.parse("https://" + USERNAME + ":" + PASSWORD + "@mail.google.com/gmail/feed/atom")["feed"]["fullcount"])
 if messages >= 1:
 # turn on big LED
 print "Turning on Big LED"
 GPIO.output(BIG_LED, True)
 big_led = 1
 print "There are", messages, "unread email messages"
 b = Repeat(1,blink,messages)
 b.start()
 else:
 print "There are no new messages"
 if big_led == 1:
 print "Turning off Big LED"
 GPIO.output(BIG_LED, False)
 sleep(60) # check the feed every minute for new mail
 print "Stopping b"
 b.stop()
 b.join()
except (KeyboardInterrupt, SystemExit):
 b.stop()
 b.join()
 GPIO.cleanup()
 print 'Program Stopped Manually!'
 raise

• flakes: I would replace Thread.__init__(self) with the super(Repeat, self).__init__() as it is a better way of calling base functions.
• flakes: Also consider breaking up larger lines into smaller portions to keep on track with PEP8's "Limit all lines to a maximum of 79 characters" rule. And use the sting.format function when surrounding strings with more text. ie) "https://{}:{}@...".format(username,password)
• Veedrac: Minor point: the try...except could quite possibly be better a try...finally.
• backwardm: Great suggestions! Thank you. I'm going to try Veedrac's structure below and look up what PEP8 says. I generally like to avoid writing long lines of code.

Answer 1

That looks about right. Your thread doesn't do very much, though, so you might want to consider something like so (untested):

def blink(abort, delay, count):
 while not abort.isSet():
 for x in range(0, count):
 print "blink", x + 1
 GPIO.output(BLUE_LED, True)
 sleep(.25)
 GPIO.output(BLUE_LED, False)
 sleep(.25)
 sleep(1) #pause between blinks
 abort.wait(delay)

Then later

thread_stop = Event()
b = threading.Thread.run(target=blink, args=(thread_stop, 1, 0))

which prevents need for the whole class. It's not a suggestion as much as a note that you did more than you needed to.

Note that your blink should really be using abort.wait and should cooperate with the other abort.wait to have sensible timings.

• backwardm: Thanks for your answer Veedrac. I'll give your suggestion a try. I didn't know about about.wait which seems like exactly what I was going for. Good to know I at least got the threading aspect right—even though it is doing very little.
• Adam: The start parameter of range defaults to zero, so you can write for x in range(count) which is the Python idiom for this scenario.