arcpy.env.workspace = r"<some/data/location>" fc = 'Parcels.shp' flyr = 'Parcels' field = 'Acres' expression = '!shape.area@acres!' try: arcpy.MakeFeatureLayer_management(fc, flyr) arcpy.AddField_management(flyr, 'Acres', 'DOUBLE') arcpy.CalculateField_management(flyr, field, expression, 'PYTHON')