os.path.join (folder, filename) ensures the path is correct for the system. On Windows, it uses backslashes (reports\summary.txt); on Linux and macOS it uses forward slashes (reports/summary.txt).

Physics and Python stuff. Most of the videos here are either adapted from class lectures or solving physics problems. I really like to use numerical calculations without all the fancy programming ...

If in the User Accounts section of the Control Panel, one that you can open by typing netplwiz.exe or control userpasswords2 in the Run command (Win+R) box, Users must enter a user name and password ...