reading mp3 tags on the www with python

I've found 开发者_如何转开发a few modules to read mp3 tags with python -- for example mutagen and id3. When doing this online, I was wondering if the modules were accessing the whole file or just the last 128 bites that contained the tag info. Thanks

Edit: When I say accessing, I mean caching to access the file data. At least that's what I think it means XD

mutagen reads last 128 bytes for id3

id3 similarly:

self.title = self.file.read(30)
self.artist = self.file.read(30)
self.album = self.file.read(30)
self.year = self.file.read(4)
self.comment = self.file.read(30)