Automatic start of python script after just plugging the power supply

Question

I am trying to make the raspberry run my python script as soon as there is power supply. I have found some ways is to prepaire the rc.local file I did and i tried to execute the rc.local file alone it works but it doesn't work when I just plug in the power supply, nor when open the puTTY session even not when I open the lxsession (It doesnt run automatically in any of the cases) my rc.local

        #!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
  printf "My IP address is %s\n" "$_IP"
fi
sudo python /home/pi/t3.py  --cascade=/home/pi/s.xml 0 
exit 0

Answer 1

this command needs a few changes to be run perfectly:

sudo python /home/pi/t3.py  --cascade=/home/pi/s.xml 0

1. get rid of sudo, rc.local is already run by superuser
2. put the complete paths there (environment might be not as you remember it)
3. add & at the end of command, because rc.local is supposed to finish fast
4. redirect outputs so your script does not get stuck when buffer is full

finally your command becomes something like:

/usr/bin/python /home/pi/t3.py --cascade=/home/pi/s.xml 0 >/dev/null &

Answer 2

You can use 'su' command instead 'sudo'. Your command should look like below. Assume that your username is 'pi'.

su pi -c '/usr/bin/python /home/pi/t3.py  --cascade=/home/pi/s.xml 0'

Answer 3

You can use cron to run a script on boot of the rpi

crontab -e

Add to the last line of the file

@reboot python /home/pi/t3.py --cascade=/home/pi/s.xml 0

From this website

Answer 4

rc.local executes as the final stage of boot. You need to wait until it would normally ask for your login credentials if a screen was plugged in. At the start of boot, nothing is ready, booting is setting everything up. You could made the boot time faster, though.