import maya.cmds as cmds
import maya.mel as mel

def init():

    arnoldSH = "light_setup:CHAR_EXT_LRIG:RIG_CTL.visibility"
    redshiftSH = "light_setup:MIFFY_LRIG_RS.visibility"
    arnoldVal = cmds.getAttr(arnoldSH)

    if arnoldVal == 1:
        cmds.setAttr(arnoldSH, 0)
        cmds.setAttr(redshiftSH, 1)
        cmds.headsUpMessage( "REDSHIFT")

    else:
        cmds.setAttr(arnoldSH, 1)
        cmds.setAttr(redshiftSH, 0)
        cmds.headsUpMessage( "ARNOLD")

init()