ModuleNotFoundError only if script is launched by cron

[Charles33]

The PATH doesn't seem that big a deal, both accounts are running "/usr/bin/python3.9". But the import path is different. The "pi" account has a .local site-packages that root isn't accessing.

I suppose something might be setting PYTHONPATH in your environment, but not in root.

Some options for you:

* Does it need to run as root? Could you put it in the "pi" user's crontab instead?
* Add "/home/pi/.local/lib/python3.9/site-packages" to PYTHONPATH in the root environment

(You could also have root install cv2 separately, but then you'd have two copies and a chance that they're not the same version. Better to keep one copy).

Thank you very much !
I could not succeed in adding PYTHONPATH in root environnment (why... If there is a good howto for that I take it !), but finally I put the crontab in the pi user and it works fine !