Labeling each polygon based on the number of points inside it using Python

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I have a parcel layer and a trees layer, I want to label each parcel with the number of trees it contains and the sum of DBH. I wrote a script that calculates this and it works stand-alone, but I can't figure out how to get it to work with a Label Expression. Here is the code I've tried (ArcMap 10.2):

import arcpyimport numpydef FindLabel(): mxd = arcpy.mapping.MapDocument("CURRENT") parcels = arcpy.mapping.ListLayers(mxd, "Parcel*")[0] trees = arcpy.mapping.ListLayers(mxd, "Surveyed Trees*")[0] arcpy.SelectLayerByLocation_management(parcels, "CONTAINS", trees, "#", "NEW_SELECTION") arcpy.SelectLayerByLocation_management(trees, "WITHIN", parcels, "#", "NEW_SELECTION") with arcpy.da.SearchCursor(trees, ["DBH"]) as cur: for row in cur: arcpy.SelectLayerByLocation_management(trees, "WITHIN", parcels, "#", "NEW_SELECTION") treeCount = int(arcpy.GetCount_management(trees).getOutput(0)) field = arcpy.da.TableToNumPyArray(trees, ("DBH"), skip_nulls = True) sum = field["DBH"].sum() message = "Trees = " + str(treeCount) + "\n" + "DBH = " + str(sum) return messageThis sends ArcMap into a long loop and then seems to return the last calculated value for each parcel, so everything is labeled "1 Tree 7 DBH".

Maybe I shouldn't be using a SearchCursor? Any advice from people more familiar with Label Expressions would be appreciated.



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