ArcGIS Script Tool RuntimeError: cannot open 'GPL0'

Question

I Cannot find what this error means or what could be causing it? Script worked until I added the lines under "Set map label to containing quad name". My environment is ArcGIS 10.1 SP1, Windows 7. Here is my code:

import arcpy

#Define I/O and workspaces
arcpy.env.workspace = "FolderPath"
arcpy.env.overwriteOutput = True
mxd = arcpy.mapping.MapDocument("MXDPath.mxd")
df = arcpy.mapping.ListDataFrames(mxd)[0]
outpath = arcpy.GetParameterAsText(2)

def getAuthCode(lon):
    if lon >= -126.0 and lon < -120.0:
        authCode = 26910 #UTM Zone 10N
    elif lon >= -120.0 and lon < -114.0:
        authCode = 26911 #UTM Zone 11N
    elif lon >= -114.0 and lon < -108.0:
        authCode = 26912 #UTM Zone 12N
    elif lon >= -108.0 and lon < -102.0:
        authCode = 26913 #UTM Zone 13N
    elif lon >= -102.0 and lon < -96.0:
        authCode = 26914 #UTM Zone 14N
    elif lon >= -96.0 and lon < -90.0:
        authCode = 26915 #UTM Zone 15N
    elif lon >= -90.0 and lon < -84.0:
        authCode = 26916 #UTM Zone 16N
    elif lon >= -84.0 and lon < -78.0:
        authCode = 26917 #UTM Zone 17N
    elif lon >= -78.0 and lon < -72.0:
        authCode = 26918 #UTM Zone 18N
    elif lon >= -72.0 and lon < -66.0:
        authCode = 26919 #UTM Zone 19N
    else:
        authCode = 4326 # WGS84
    return authCode

#Create extent/spatial referenece objects
lat = arcpy.GetParameterAsText(0)
lon = arcpy.GetParameterAsText(1)
WGS84 = arcpy.SpatialReference(4326) #Creates spatial reference variable to switch back to later
UTM = arcpy.SpatialReference(getAuthCode(lon))
df.spatialReference = WGS84 #Set spatial reference to WGS84
resetPT = arcpy.Extent(-97.747957, 30.280553, -97.747957, 30.280553)

#Set map label to containing quad name
point = arcpy.Point(lon, lat)
ptGeo = arcpy.PointGeometry(point, WGS84)
quadPath = "LayerPath.lyr"
quadLyr = arcpy.mapping.Layer(quadPath) #arcpy.mapping.ListLayers(mxd)[0]
selectedLyr = arcpy.SelectLayerByLocation_management(quadLyr, "INTERSECT", ptGeo)
cursor = arcpy.da.SearchCursor(selectedLyr, "QUAD_NAME")
quadName = ""
for row in cursor:
    quadName = str(row)
label = arcpy.mapping.ListLayoutElements(mxd, "TEXT_ELEMENT", "Label")[0]
label.text = "NWI Map" + "\n" + "Quad: " + quadName[3:-3] + ", TX"
label.elementPositionX = 0.3
label.elementPositionY = 0.3

#Pans to centerpoint and sets scale to 1:12000
extent = arcpy.Extent(lon, lat, lon, lat)
df.panToExtent(extent)
df.spatialReference = UTM #Temporarily set spatial reference to correct UTM zone
df.scale = 12000
arcpy.RefreshActiveView()

#Export map to ES# folder
arcpy.mapping.ExportToPDF(mxd, outpath, resolution=300) #exportToPDF

#Reset extent/spatial reference
df.spatialReference = WGS84 
df.panToExtent(resetPT)
arcpy.RefreshActiveView()

mxd.save()

Answer 1

Your error is essentially saying that it can't open the layer file due to the manner in which you provided it. Esri loves cryptic errors like that.

If you're running this as a Script Tool, I suspect the issue is with the manner in which you reference the quadPath variable. That's not a normal way to reference a layer file saved on disk. The way you're doing it is what I typically see when people are working with the Python Window, because the Python Window has a built-in list of all the items in the Table of Contents and there it references items in that built-in list according to their namespace.

Try referencing that Layer file using its absolute path instead.

Answer 2

Figured it out. The SelectLayerByLocation method changes the state of the quadLyr object, so instead of assigning the method to selectedLyr I ran the method and then used quadLyr as input for the cursor.