calling external function with arguments

[Liliana]

If I call it from another python program the arguments are not found, I cannot figure out how to pass the arguments. How to do?

I may think there is confusion about using command line tool sys.argv, getopt(do not use as mention).
Because you don't use command line here at all,but try to call it from a other module using a string. tiny fishing

argparse Gribouillis show is ok,but can show a example with Typer which is really cool.
Here i also do rename on files on disk,not just show there names.

from pathlib import Path
import typer

app = typer.Typer()

@app.command()
def renameit(
    old_name: str = typer.Option(..., '-o', '--old-name'),
    new_name: str = typer.Option(..., '-n', '--new-name'),
):
    old_path = Path(old_name)
    if old_path.is_file():
        old_path.rename(Path(new_name))
        typer.echo(f'File renamed from {old_name} to {new_name}')
    else:
        typer.echo('File not found.')

if __name__ == '__main__':
    app() 

Using it,see that help and colors get(use Rich under the hood) get generated automatic.

Also using this in a other module only need to pass app,and it will work.

from rename_files import app

if __name__ == '__main__':
    app()

Thanks, it works.