The following code contains more than you need, but it will show that you need to specify or create a blank mxd, then specify a data frame, then activate that data frame then add your layers/shapefiles with optional symbology specified
'''
mxd_create.py
Author: [email protected]
Purpose: create a base mxd and populate it with default values
Requires: specify the files to load and the default dataframes etc
template paths
ie
C:\Program Files (x86)\ArcGIS\Desktop10.2\MapTemplates\Traditional Layouts\LetterLandscape.mxd
C:\Program Files (x86)\ArcGIS\Desktop10.2\MapTemplates\Traditional Layouts\LetterPortrait.mxd
'''
import arcpy
import sys
import os
import shutil
script = sys.argv[0] # script name and location
mxd_src = "C:/!test/mapping/mxd_test02.mxd" # a shell empty project
path, doc = os.path.split(mxd_src)
template = path + "/LetterPortrait.mxd"
shutil.copyfile(template,doc)
arcpy.env.workspace = path + "/shapefiles"
arcpy.overwriteOutputs = True
shp_files = ["AOI_mtm9.shp", "RandomPnts.shp"]
lyr_files = ["AOI_mtm9.lyr","RandomPnts.lyr"]
arcpy.ListFiles("*.lyr") #use this to check above
author = "This could be you!!!!"
description = "Demo project working with the arcpy.mapping module and Python"
title = "Arcpy Mapping Demo: Introduction to arcpy.mapping and Python interaction"
mxd = arcpy.mapping.MapDocument(doc)
mxd.author = author
mxd.description = description
mxd.title = title
mxd.relativePaths = True
df = arcpy.mapping.ListDataFrames(mxd)[0] # list of data frames, 1 exists by default
df.name = "Sample files" # set its title
mxd.activeView = df.name # activate it
for shp in shp_files: # cycle through the list of shapefiles
#fn, ext = os.path.splitext(f) # for testing
lyr = arcpy.mapping.Layer(shp) # add the files and auto arrange
arcpy.mapping.AddLayer(df,lyr,"AUTO_ARRANGE")
arcpy.ApplySymbologyFromLayer_management(lyr,lyr_files[1]) # apply symbology from lyr files
#arcpy.mapping.UpdateLayer(df, updateLayer, sourceLayer, True)
arcpy.RefreshActiveView()
mxd.save()
del template, shp_files, lyr_files, lyr, df, mxd
os.startfile(doc)
del doc
##
Hope this helps
