If you have a P3IO from a jubeat or GuitarFreaks/DrumMania PC, you can do some microsoldering to convert it to the typical DDR P3IO, at which point it will work out of the box with PC-based DDR mixes without any hooks.
Cut two traces and solder two jumper wires as shown in the following photo:
You will have to solder a 3 pin JST header on CN21. Then make a bridge to where the old COM2 were on the 6 pin JST next to it. This will put the cardreaders on the exact same spot as where it was on the Python 2. You now have a plug and play P3IO for DDR!
credit for instructions + images: GravitySandwich