#CONSTRAINT
direction = cont.actuators['Direction'] #the constraint actuator
face = sce.objects['Facer'] #the facing object
faco = face.localOrientation[1] #here we are (this gives me a 3x3 matrix)
                                #but i only want to use the Y value
                                #I’ve tried out even 0, and 2 but wont work

def constra():
    direction.direction = faco #this isn't running as it should
    cont.activate(direction)

import bge
import mathutils

sce = bge.logic.getCurrentScene()
face = sce.objects['Facer']
facY = face.worldOrientation.to_euler()[1] #Now we have the Y-axis rotation
facTar = sce.objects['Facingtarget']       #This is the target object we modify
newRotList = [facTar.worldOrientation.to_euler()[0],facY,facTar.worldOrientation.to_euler()[2]] #Now we have a list
newRot = mathutils.Euler(newRotList).to_matrix()   #Now we have the matrix we need
facTar.worldOrientation = newRot    #The orientation has been modified