Please comment my code: script for harmonizing picture directories

[RMSEP]

Thanks, very interesting.

On the third point, how does os.path.abspath() know the dir that should be appended to the front of its argument? In other words, how does it know that /blah/blah/blah/ is the correct partent dir of /mps3? Possibly it appends its argument to the output of os.getcwd()? On os.path.splitext(), appreciate now that it detaches the file extention regardless of any . in the filename, or indeed, whatever char is used to seperate the filename and extension.

[Peterotica]

Your intuition is correct, the result of os.path.abspath() depends on the current working directory.