Problem Setting Label Expression in Arcpy

JonathanMulder

I'm trying to set a label expression to a field ("StateWellNumber") in my table.  I have the following code but I get an error message saying "name 'StateWellNumber' is not defined".

Any ideas?

Jon Mulder

LayerFileLocation = "H:\Documents\GIS\HydstraData" LayerName = "WellPoints.lyr" ##Show labels for WellPoints. arcpy.mapping.Layer(os.path.join(LayerFileLocation,LayerName)).supports("LABELCLASSES") arcpy.mapping.Layer(os.path.join(LayerFileLocation,LayerName)).showLabels = True arcpy.mapping.Layer(os.path.join(LayerFileLocation,LayerName)).labelClasses.expression =  [StateWellNumber] 

JoshuaChisholm

Sorry I should have caught that.

lyr.labelClasses is an array (list) of multiple labelClass items. Changes are it is a array of 1 item(s).

The '.expression' variable can be used on a single labelClass (not an array or 'list' of labelClasses). You have two (at least) choices:

One; you can assume your layer only has one labelClass (this is likely the case) and apply the expression to the first one. Keep in mind that arrays start at 0 not 1.

lyr.labelClasses[0].expression =  "[StateWellNumber]"

Two; you can apply the expression to all labelClasses in the layer. You'll need to remove the line lyr.labelClasses.expression =  "[StateWellNumber]" and add a for loop.

for labelClass in lyr.labelClasses:     labelClass.expression = "[StateWellNumber]"

Hope that helps!!