I've never tried labeling through
arcpy myself, but it appears that you can enable and edit labels via the
arcpy.mapping module as described here. The basics of the mapping module are:
1) Create a reference to a map document (if it is open in ArcMap, you can use "CURRENT")
2) Create a reference to the data frame(s) in the map document (optional)
3) Create a reference to the layer(s) in the data frame(s)
These references all act as objects which can be used in any geoprocessing as inputs and outputs as long as they are of the proper type. Initially they will be lists, so be sure to INDEX the reference! For labeling, if you know exactly which layer you want to label, it appears that you could use the following code:
mxd = arcpy.mapping.MapDocument(r"Mypathhere") #Map document reference
layer = arcpy.mapping.ListLayers(mxd, "Layername") #Indexing list for 1st layer
for lblclass in layer.labelClasses:
lblclass.className = "Class Name Here"
lblclass.expression = "Labeling expression here"
lblclass.showClassLabels = True
And done. The
arcpy.mapping module/class gives a ton of functionality for programmatic MXD customization. Give it a good looking over, I'm sure you will find it useful.