Fails to same Python script from Terminal/Automator/Script Editor

You copy/paste the actual source code content of your script inside the Python HERE document right after the import statements. You don't select it to pass into the Run Shell Script action. You don't need that print statement that I used for the previous example.

When you run Python in an Automator Run Shell Script, or Run AppleScript action, it is running Python 2.7.16, the default Python installation on macOS, because it hasn't a clue where Python3 is installed.

In order to run Python3 in an Automator Run Shell Script action, you need to use HERE syntax like the following in a Bash or Zsh shell:

Your PATH and environment variables are extremely limited.

write an automator app with

printenv >~env.txt

save the app, and run it. Then look at env.txt

When you create your python script, compensate for any missing PATH directories and environment variables your python script my need

You didn't follow the example exactly as your Passa a input: is set to come stdin, not as arguments. You will need to change that so you can pass the results from the previous action into your Python3 script code as sys.argv[1]. The only purpose of my example was to confirm the path to the Python3 (3.9.5) library.

What is the file that you have selected? Is it a Python module of some kind?

You are welcome. Working properly?