I looked into it a bit more. With python 2.7 on macOS High Sierra on APFS (Encrypted) with a FAT32 thumb drive... I have a directory that glob.glob('/Volumes/thumb/tmp/*') shows as sorted. I cp -r that to /tmp with bash. glob.glob('/tmp/tmp/*') is now not sorted. and cp -r /tmp/tmp /Volumes/thumb/tmp1. Then glob.glob('/Volumes/thumb/tmp/*') shows a different order, but if I cp -r /Volumes/thumb/tmp/ /Volumes/thumb/tmp2 then glob.glob('/Volumes/thumb/tmp2/*') is sorted by file name just like glob.glob('/Volumes/thumb/tmp/*'). I'm not sue what that's saying other than that glob.glob can return things out of order on FAT32. It appears that glob.glob's ordering agrees with that of ls -f ("unsorted").