change texture info

#change texture info
from pymel.core import *
sl = selected()
matTypeList = ["lambert","blinn","phong"]
fileType = "jpg"
for s in sl:
    sg = s.getShape().listConnections()[0]
    sM = sg.listConnections(type = "lambert")[0]
    sT = listConnections(str(sM)+".color")
    sTfile = getAttr(sT[0]+".fileTextureName")
    sTfile = sTfile[:-3]+fileType
    setAttr(sT[0]+".fileTextureName", sTfile)
    print sTfile