Help with relay

[corminos]

I have a 12v relay hooked up to my Raspberry Pi 4. I am able to turn an LED light off and on by running the command "python3" then setting a GPIO pin to LOW and HIGH. This all works great.

Here is what I run from the command line:

pi@retropie:~ $ python3
Python 3.7.3 (default, Dec 20 2019, 18:57:59)
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import RPi.GPIO as GPIO
>>> GPIO.setmode(GPIO.BCM)
>>> PIN_1 = 23
>>> GPIO.setup(PIN_1, GPIO.OUT)
>>> GPIO.output(PIN_1, GPIO.LOW)
>>> GPIO.output(PIN_1, GPIO.HIGH)
>>> GPIO.cleanup()
>>> exit()

But, when I put the code into a script and run the script with a sudo command, nothing happens.

Below is the script. I run it using "sudo ./light.py on"

My question is why isn't the script running? What is the difference between running a script and entering the command by just running "python3"?

#!/usr/bin/env python3

"""
A script to turn the relay off and on
"""

usage = """
Usage: light.py [on|off]

Takes a single argument which should be either "on" (turn lights on) or "off" (turn them off)
"""

import sys

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)

PIN_1 = 22
PIN_2 = 23

GPIO.setup(PIN_1, GPIO.OUT)
GPIO.setup(PIN_2, GPIO.OUT)

def turn_off():
  print("turning off")
  GPIO.output(PIN_1, GPIO.HIGH)
  GPIO.output(PIN_2, GPIO.HIGH)

def turn_on():
  print("turning on")
  GPIO.output(PIN_1, GPIO.LOW)
  GPIO.output(PIN_2, GPIO.LOW)

mode = sys.argv[1]

print(mode)

if mode not in ("on", "off"):
  print("Invalid argument!", file=sys.stderr)
  print(usage)
  GPIO.cleanup()
  sys.exit(1)

if mode == "on":
  turn_on()
elif mode == "off":
  turn_off()

GPIO.cleanup()
sys.exit()

I do get the output from the "print" statements, so I know the code is getting into the defined methods.

Thanks in advance.

[corminos]

Sorry, I shouldn't have said "why isn't the script running?" What I should have said was "Why isn't the script turning on and off the relay?"

Also, I had another script that I would test the state of the pin and this would toggle the output from reading the GPIO pin as I ran the light.py script.

#!/usr/bin/env python3

import RPi.GPIO as GPIO
import sys

channel = int(sys.argv[1])

GPIO.setmode(GPIO.BCM)
# Setup your channel
GPIO.setup(channel, GPIO.OUT)

# To test the value of a pin use the .input method
channel_is_on = GPIO.input(channel)  # Returns 0 if OFF or 1 if ON

if channel_is_on:
 print('it is on')
else:
 print('it is off')

GPIO.cleanup()
sys.exit()

[corminos]

One more piece of the puzzle...at the end of my script, if I remove the GPIO.cleanup(), then the light stays on.

But, in subsequent calls to my script, I receive a warning that the channel is already in use. It doesn't stop the code, but the programmer in me doesn't like warnings.

My question now is why does the cleanup function change the output of the GPIO pins?