How do you embed album art into an MP3 using Python?

Question

Here is how to add example.png as album cover into example.mp3 with mutagen:

from mutagen.mp3 import MP3
from mutagen.id3 import ID3, APIC, error

audio = MP3('example.mp3', ID3=ID3)

# add ID3 tag if it doesn't exist
try:
    audio.add_tags()
except error:
    pass

audio.tags.add(
    APIC(
        encoding=3, # 3 is for utf-8
        mime='image/png', # image/jpeg or image/png
        type=3, # 3 is for the cover image
        desc=u'Cover',
        data=open('example.png').read()
    )
)
audio.save()

I've used the eyeD3 module to do this exact thing.

def update_id3(mp3_file_name, artwork_file_name, artist, item_title):    
    #edit the ID3 tag to add the title, artist, artwork, date, and genre
    tag = eyeD3.Tag()
    tag.link(mp3_file_name)
    tag.setVersion([2,3,0])
    tag.addImage(0x08, artwork_file_name)
    tag.setArtist(artist)
    tag.setDate(localtime().tm_year)
    tag.setTitle(item_title)
    tag.setGenre("Trance")
    tag.update()

Looks like you have to add a special type of frame to the MP3. See the site on ID3 tags

Also the tutorial for mutagen implies that you can add ID3 tags in mutagen see

Possible solution

Are you trying to embed images into a lot of files? If so, I found a script (see the link) that goes through a set of directories, looks for images, and the embeds them into MP3 files. This was useful for me when I wanted to actually have something to look at in CoverFlow on my (now defunct) iPhone.