Then you need to learn how to run python code from a command-line argument instead of from a script. That’s a python question, not a Notepad++ question.

The Notepad++ specific part of your question is how to access the selection in an NppExec script (or Run command), and you now have that information.

Though I’ll thow you a fish: if you can figure out how to use Notepad++'s default plugins, then cHl0aG9uIC1jICJwcmludCgkKENVUlJFTlRfV09SRCkpIg can be easily decoded to hand you the answer. But any further questions about how to use python.exe are off topic here.

$(CURRENT_WORD) works in NppExec (or the Run menu’s Run… command) to give the contents of the active selection. This is documented in the Plugins > NppExec > Docs > NppExec_HelpAll.txt (and NPP User Manual > Config Files > User Defined Commands)