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).

Answer 1

Variable "theShape" is the path of the shape file to be added.

import arcpy
import arcpy.mapping
# get the map document 
mxd = arcpy.mapping.MapDocument("CURRENT")  

# get the data frame 
df = arcpy.mapping.ListDataFrames(mxd,"*")[0]  

# create a new layer 
newlayer = arcpy.mapping.Layer(theShape)  

# add the layer to the map at the bottom of the TOC in data frame 0 
arcpy.mapping.AddLayer(df, newlayer,"BOTTOM")

# Refresh things
arcpy.RefreshActiveView()
arcpy.RefreshTOC()
del mxd, df, newlayer

Answer 2

Recently I struggled with a similar task, and initially used the method of identifying the map document, identifying the data frame, creating a layer and adding the layer to the map document. Interestingly enough, this can all be accomplished using the following provided it is called from within the current map document.

# import modules
import arcpy

# create layer in TOC and reference it in a variable for possible other actions
newLyr = arcpy.MakeFeatureLayer_managment(
    in_features, 
    out_layer
)[0]

Make Feature Layer requires two inputs, the input features and the output layer. The input features can be any type of feature class or layer. This includes shapefiles. Output layer is the name of the layer to appear in the table of contents.

Also, Make Feature Layer can accept a where clause to create a definition query at creation time. This typically is how I implement it, when needing to create a lot of layers with different definition queries quickly.

Finally, in the above snippet, although it is not necessary, I demonstrated how to populate a variable with the result of the tool output so the layer could be manipulated in the table of contents using arcpy.mapping if this is necessary later in the script. Every tool returns a result object. The result object output can be accessed using the getOutput method, but it can also be accessed by using the index of the result property you are interested in, in this case the output located at index 0.