dxfout.py

import Part,Drawing,FreeCADGui,FreeCAD
from FreeCAD import Base
filename = "/home/danfalck/Documents/freecad/test20120209-1.dxf"
FILE = open(filename,"w")
sel = FreeCADGui.Selection.getSelection()
sel = sel[0]
shape = sel.Shape
dxf_output = Drawing.projectToDXF(shape,Base.Vector(0,0,1))
FILE.write(dxf_output)
FILE.close()