I am attempting to turn a layer on in the Layer of Contents via a python script. When I execute the script below either as a script tool in ArcToolbox or via the python window in ArcMap the visibility status changes in the layer properties but the layer does not turn on in the Table of Contents and the layer does not draw in the data view window. I execute this script within ArcMap and have layers in the Table of Contents which are currently turned off.
# Import arcpy module
from arcpy import env
mxd = arcpy.mapping.MapDocument("CURRENT")
df = arcpy.mapping.ListDataFrames(mxd, "")
for lyr in arcpy.mapping.ListLayers(mxd, "", df):
lyr.visible = True