Fan controller for pi

#! /usr/bin/env python3
import os
import RPi.GPIO as GPIO
import time
import datetime
import sys

# 5 * * * * sudo python /home/pi/fan.py
# A crontab will run every hour and check the temp. If the temp is > 49 the script will start the fan
# until the temperature goes down to 28. When it does, the script will end, shutting down the fan as well.
# If the script executes again while a previous script is running, the latter will exit
# ... meaning the pi is in hell, and will never get bellow FAN_END value :P

# Identify which pin controls the relay
FAN_PIN = 18 # the yellow box ex: GPIO18
# Temperature check. Start fan if temp > 49C
FAN_START = 49
# Temperature check. Shut down under 28C
FAN_END = 28

# Get what action. If you manually turning on/off the fan
action = sys.argv.pop()


def GPIOsetup():
    GPIO.setwarnings(False)
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(FAN_PIN, GPIO.OUT)

def fanON():
    GPIOsetup()
    GPIO.output(FAN_PIN, 0) #fan on
    return()
def fanOFF():
    GPIOsetup()
    GPIO.output(FAN_PIN, 1) #fan off
    return()

def get_temp_from_system():
    res = os.popen('vcgencmd measure_temp').readline()
    return(res.replace("temp=","").replace("'C\n",""))

def check_fan(pin):
    GPIOsetup()
    return GPIO.input(pin)

def run(pin):
    current_date = datetime.datetime.now()
    temp = get_temp_from_system()
    if float(temp) >= FAN_START:
        print(temp+' @ '+str(current_date))
        if check_fan(pin) == 1:
            print('Fan is Off...Starting Fan')
            fanON()
        else:
            time.sleep(5) # Remove, if you want real-time checking
            print('Fan is ON')
    elif float(temp) <= FAN_END:
        print(temp+' @ '+str(current_date))
        if check_fan(pin) == 0:
            print('Fan is on...Shuting it Down')
            fanOFF()
            GPIO.cleanup()
            return 1 # exit script. The pi has cooled down
        else:
            time.sleep(5) # Remove, if you want real-time checking
            print('Fan is OFF')
    else:
            pass # while the script is passing through here, there will be no output on screen


if action == "on" :
   print "Turning fan on"
   fanON()
elif action == "off" :
   print "Turning fan off"
   fanOFF()

# first check if script is already running
if check_fan(FAN_PIN) == 0:
    print('Fan is on, script must be running from another instance...')
else:
    temp = get_temp_from_system()
    if float(temp) < FAN_START:
        print('Pi is operating under normal temperatures.')
    else:
        try:
            while(True):
                tmp = run(FAN_PIN)
                if tmp == 1: # value returned from line 60
                    break
        except KeyboardInterrupt:
            fanOFF()
            GPIO.cleanup()
        finally:
            fanOFF()
            GPIO.cleanup()