Add cover to ID3v2 tags

addcover.py

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

audio = MP3('music.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/jpeg', # image/jpeg or image/png
        type=3, # 3 is for the cover image
        desc=u'Cover',
        data=open('image.jpg', 'rb').read()
    )
)

audio.save(v2_version=3) # for supporting Windows Media player