py: vertex transparency how?

Hey you specialists!
How can I make Blender use my alpha values in vertex colors?

I tried this script, but no result.
Are there any special settings in the materials?

I didn’t found anything in Google so probably you can help me.

thanks

fritz

from Blender import *
from Blender.NMesh import *
from Blender.Material import *
me = NMesh.GetRaw() 
f = NMesh.Face()
v = NMesh.Vert(-1.0, 0.0, 0.0)
me.verts = [v]
f.v = [v]

v = NMesh.Vert(1.0, 0.0, 0.0)
me.verts.append(v)
f.v.append(v)

v = NMesh.Vert()
v.co[0] = 0.0; v.co[1] = 1.0; v.co[2] = 0.0
me.verts.append(v)
f.v.append(v)

f.col = [Col(255,0,0,0), Col(0,255,0,128), Col(0,0,255,0)]
f.transp = NMesh.FaceTranspModes['ALPHA']

me.faces=[f]
me.hasVertexColours(1)
newmat = Material.New()
newmat.mode |= Material.Modes.VCOL_PAINT
me.materials.append(newmat)

NMesh.PutRaw(me)
Redraw()