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).

Mortgages have downshifted a bit from highs earlier in the week but continue to fluctuate with the latest economic news. Retail sales were up more than expected, and jobless claims were down, showing ...