How do I add a shapefile in ArcGIS via python scripting?

Question

I am trying to automate various tasks in ArcGIS Desktop (using ArcMap generally) with Python, and I keep needing a way to add a shape file to the current map. (And then do stuff to it, but that's another story).

The best I can do so far is to add a layer file to the current map, using the following ("addLayer" is a layer file object):

def AddLayerFromLayerFile(addLayer):
 import arcpy
 mxd = arcpy.mapping.MapDocument("CURRENT")
 df = arcpy.mapping.ListDataFrames(mxd, "Layers")[0]
 arcpy.mapping.AddLayer(df, addLayer, "AUTO_ARRANGE")
 arcpy.RefreshActiveView()
 arcpy.RefreshTOC()
 del mxd, df, addLayer

However, my raw data is always going be shape files, so I need to be able to open them. (Equivantly: convert a shape file to a layer file wiothout opening it, but I'd prefer not to do that).