$disc support

I had a play adding disc_number to fileops.py:
-added ,'disc' to metatypes @ line 14
-inserted metatypes[4] ... PROP_DISC_NUMBER @ line 27

this seems simple enough, but it would cause an error in tools.py
-AttributeError: 'int' object has no attribute 'replace',
which i assume means the disc property in metadata isn't coming across correctly?

The error is in "process (string)"
if i add string = `string` that will bypass the error but then the only metadata that comes out correctly when moving is disc number. Maybe an if statement would be better.

This is how i organise my music, Multiple discs are stored in the same folder and disc number helps sort them which is why i had a go mysefl.
~\music\$artist\($year) $album\$disc$track - title

Is what i'm thinking the right way of doing it, or is there an added issue adding disc number compared to track number?
I only have basic python knowledge but I think this is a great plugin for rhythmbox to have. :)