I've been using mutagen for reading and writing MP3 tags, but I want to be able to embed album art directly into the file.
A nice small CLI tool which helped me a lot with checking what I did while developing id3 stuff is mid3v2 which is the mutagen version of id3v2. It comes bundled with the Python mutagen library. The source of this little tool gave me also lots of answers about how to use mutagen.
How do you embed album art into an MP3 using Python?