Not the greatest fan of python, but when I've got to run a python script, I do `nix-shell -p 'python3.withPackages (ps: [ps.requests])' --command 'python3 your-script.py'` Note that there is one argument to -p and one argument to --command -- both are quoted. The argument to -p is a nix expression that will provide a python3 command, referring to a python3 with the requests package. The argument to --command is a bash script that will run python3 with the argument "your-script.py" i.e. it will run your-script.py with the python3 that has the requests package.

I think there's ways you can autoderive a python3 with specific packages from python dependency files, but I can't help you there. I do find AI to be reasonably helpful for answering questions like this: it just might sometimes require a bit of help that you want to understand the answer rather than receive a perfect packaged shell.nix file.