bash - Launch a python script from another script, with parameters in subprocess argument

Question

To launch a python script (it is needed for running an OLED display) from terminal, I have to use the following bash commands: python demo_oled_v01.py --display ssd1351 --width 128 --height 128 --interface spi --gpio-data-command 20. Those parameters after .py are important, otherwise, the script will run with default settings and in my case, the script will not launch with default settings. Thus, those parameters are needed.

The problem arises when I need to launch my script from another python script, (instead of using bash commands on terminal). To launch one of my python script from a parent script. I have used:

import subprocess # to use subprocess 

p = subprocess.Popen(['python', 'demo_oled_v01.py --display ssd1351 --width 128 --height 128 --interface spi --gpio-data-command 20'])

in my parent script but I got an error stating:

python: can't open file 'demo_oled_v01.py --display ssd1351 --width 128 --height 128 --interface spi --gpio-data-command 20': [Errno 2] No such file or directory

I suspect that adding the parameters --display ssd1351 --width 128 --height 128 --interface spi --gpio-data-command 20 after .py may be causing difficulty in launching the script. As mentioned, these parameters are otherwise essential for me to include for launching with bash commands on terminal. How can I use subprocess with the required parameters to launch this script?

Answer 1

The subprocess library is interpreting all of your arguments, including demo_oled_v01.py as a single argument to python. That's why python is complaining that it cannot locate a file with that name. Try running it as:

p = subprocess.Popen(['python', 'demo_oled_v01.py', '--display',
'ssd1351', '--width', '128', '--height', '128', '--interface', 'spi',
'--gpio-data-command', '20'])

See more information on Popen here.