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()

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Imports
from mutagen.id3 import ID3, TRCK, TIT2, TPE1, TALB, TDRC, TCON, COMM

# Set file
audio = ID3("example.mp3")

# Add tags
audio.add(TRCK(encoding=3, text=u"1"))
audio.add(TIT2(encoding=3, text=u"Title"))
audio.add(TPE1(encoding=3, text=u"Artist"))
audio.add(TALB(encoding=3, text=u"Album"))
audio.add(TDRC(encoding=3, text=u"2011"))
audio.add(TCON(encoding=3, text=u"Genre"))
audio.add(COMM(encoding=3, lang="eng", desc="", text="Comment"))

# Save tags
audio.save()

# Print tags
print audio.pprint()

audio = ID3(u'P:/How Low_2.mp3')
pic = APIC(3, u'image/jpg', 3, u'Front cover', open(u'cover.jpg', 'rb').read())
audio.add(pic)
audio.save()

import mutagen.[format]
metadata = mutagen.[format].Open(filename)

4.14.   Attached picture

   This frame contains a picture directly related to the audio file.
   Image format is the MIME type and subtype [MIME] for the image. In
   the event that the MIME media type name is omitted, "image/" will be
   implied. The "image/png" [PNG] or "image/jpeg" [JFIF] picture format
   should be used when interoperability is wanted. Description is a
   short description of the picture, represented as a terminated
   text string. There may be several pictures attached to one file, each
   in their individual "APIC" frame, but only one with the same content
   descriptor. There may only be one picture with the picture type
   declared as picture type $01 and $02 respectively. There is the
   possibility to put only a link to the image file by using the 'MIME
   type' "-->" and having a complete URL [URL] instead of picture data.
   The use of linked files should however be used sparingly since there
   is the risk of separation of files.

     <Header for 'Attached picture', ID: "APIC">
     Text encoding      $xx
     MIME type          <text string> $00
     Picture type       $xx
     Description        <text string according to encoding> $00 (00)
     Picture data       <binary data>


   Picture type:  $00  Other
                  $01  32x32 pixels 'file icon' (PNG only)
                  $02  Other file icon
                  $03  Cover (front)
                  $04  Cover (back)
                  $05  Leaflet page
                  $06  Media (e.g. label side of CD)
                  $07  Lead artist/lead performer/soloist
                  $08  Artist/performer
                  $09  Conductor
                  $0A  Band/Orchestra
                  $0B  Composer
                  $0C  Lyricist/text writer
                  $0D  Recording Location
                  $0E  During recording
                  $0F  During performance
                  $10  Movie/video screen capture
                  $11  A bright coloured fish
                  $12  Illustration
                  $13  Band/artist logotype