m4a file tagger. Especially used as subroutine for to extract tags from file name.

m4atag

#!/usr/bin/env python
# Author: Zigang Xiao <iveney # gmail.com>
# Date  : 07/12/2011

"""A python utility (wrapper for mutagen.m4a) to udpate tags for m4a file type.

Relies on m4a module in mutagen.
"""

from mutagen.m4a import M4A
from sys import argv
from string import atoi
import argparse

tags = {'album'  : '\xa9alb',
        'artist' : '\xa9ART',
        'year'   : '\xa9day',
        'title'  : '\xa9nam',
        'comment': '\xa9cmt',
        'group'  : '\xa9grp',
        'writer' : '\xa9wrt',
        'genre'  : '\xa9gen',
        'track'  : 'trkn',
        'aart'   : 'aART',
        'disk'   : 'disk',
        'cpil'   : 'cpil',
        'tempo'  : 'tmpo',
        }

class ParsePair(argparse.Action):
    def __call__(self, parser, namespace, values, option_string=None):
        try:
            values = map(int, values.split('/'))
            if len(values) == 1:
                values = values + [0]
            elif len(values) > 2:
                raise
        except:
            print "Error: format should be 'num/num'"
            parser.print_help()
            exit(1)
        setattr(namespace, self.dest, values)

class ParseYesNo(argparse.Action):
    def __call__(self, parser, namespace, values, option_string=None):
        values = (values == 'y')
        setattr(namespace, self.dest, values)

def get_args():
    parser = argparse.ArgumentParser(description = 'm4a/aac tag updater')
    parser.add_argument('-a', '--artist', 
            help = 'artist name')
    parser.add_argument('-A', '--album',
            help = 'album name')
    parser.add_argument('-y', '--year',
            metavar = 'YYYY',
            help = 'set the year')
    parser.add_argument('-t', '--title',
            help = 'song title')
    parser.add_argument('-T', '--track', 
            metavar = 'num/num',
            help = 'set the number/(optional) total tracks',
            action = ParsePair)
    parser.add_argument('-c', '--comment',
            help = 'set the comment')
    parser.add_argument('-G', '--group',
            help = 'set the grouping')
    parser.add_argument('-w', '--writer',
            help = 'set composer')
    parser.add_argument('-g', '--genre',
            help = 'set genere')
    parser.add_argument('--aart', 
            help = 'set album artist')
    parser.add_argument('-d', '--disk',
            help = 'set the disk/(optional) total disks',
            action = ParsePair)
    parser.add_argument('-C', '--cpil',
            help = "set is part of a compilation",
            choices = 'yn',
            action = ParseYesNo)
    parser.add_argument('--tempo', type = int,
            help = 'set tempo')
    parser.add_argument('filename', 
            help = 'The input file')
    return vars(parser.parse_args())

if __name__ == '__main__':
    args = get_args()

    audio = M4A(args['filename'])
    for key in args:
        if key == 'filename' or args[key] == None:
            continue
        tag = tags[key]
        value = args[key]
        if type(value) == str:
            value = unicode(value, 'utf8')
        #print key, tag, value, type(value)
        audio[tag] = value
    audio.save()