changes to accomodate potential comment lines in files

added comments to code

relative-playlist-maker.py

@@ -1,39 +1,57 @@
 from argparse import ArgumentParser
+from itertools import filterfalse
 from pathlib import Path
 from logging import basicConfig, warning, WARNING
 from shutil import copyfile
 
 def main(music_folder: Path):
+    # get the absolute path of the music folder from the argument
     music_folder = music_folder.resolve().absolute()
 
+    # recursively traverse music_folder looking for .m3u files and, for each, ...
     for m3u in music_folder.rglob("*.m3u"):
+        # create a copy in the same directory as a backup
         copyfile(m3u, m3u.with_suffix(".m3u.bak"))
 
+        # read the contents of the file
         with m3u.open("r") as contents:
-            tracks = [Path(p) for p in contents.readlines()]
-
+            lines = contents.readlines()
+        
+        # check that all non-comment lines refer to files in the music directory
         if not all(
-            music_folder in track.parents 
-            if track.is_absolute() 
-            else music_folder in m3u.parent.joinpath(track).resolve().parents
-            for track in tracks
+            music_folder in Path(line).parents 
+            if Path(line).is_absolute() 
+            # join the parent path to the relative path in line, then resolve out the relative parts
+            else music_folder in m3u.parent.joinpath(Path(line)).resolve().parents
+            # ignore lines which start with # because they are comments, not paths to tracks
+            for line in filterfalse(lambda l: l.strip().startswith("#"), lines)
         ):
+            # if the file contains references to files outside of the music folder, skip the m3u file and continue to the next one
             warning(f"{m3u} contains references to tracks that are not in {music_folder} and will be skipped")
             continue
        
         with m3u.open("w") as updated_contents:
-            for track in tracks:
-                if track.is_absolute():
-                    updated_contents.write(track.relative_to(m3u, walk_up=True).as_posix())
+            for line in lines:
+                # comment line.  just write it.
+                if line.strip().startswith("#"):
+                    updated_contents.write(line)
+                # line contains an absolute path
+                elif Path(line).is_absolute():
+                    # get the path of the track file relative to the playlist file and write it in posix form (/ is path delimiter)
+                    updated_contents.write(Path(line).relative_to(m3u, walk_up=True).as_posix())
+                # line already contains a relative path
                 else:
-                    updated_contents.write(track.as_posix())
+                    # normalize as a posix path
+                    updated_contents.write(Path(line).as_posix())
 
 
 if __name__ == "__main__":
+    # setup logging to terminal
     basicConfig(
         level=WARNING,
     )
     
+    # setup a parser for the CLI
     parser = ArgumentParser(
         description="Recursively traverse a music folder containing tracks and playlist files that reference them, replacing absolute paths in the playlists with equivalent relative paths."
     )
@@ -44,6 +62,7 @@ if __name__ == "__main__":
         type=Path
     )
 
+    # parse the command line for the one and only argument
     args = parser.parse_args()
 
     main(args.music_folder)