I have seen several similar posts related to this technique but I am still having issues. The following script is intended to select all points from one shapefile that are within the boundaries of a second polygon shapefile, then edit the number of points selected into one of the polygon fields. I have not been able to get the where clause statement to function properly although from the error message it appears to be correct. Both shapefiles are within a file geodatabase and feature layers where created for both in order to use the selection functions.

Here is the code:


for row in cursor:
    where='"map_name"' + '=' + '\'' + str(map) + '\''
    row.setValue('DI_Count', count)

Here is the error statement:

Executing: SelectLayerByAttribute maps NEW_SELECTION "map_name"='Airport'
Start Time: Wed Jan 15 13:00:56 2014
ERROR 000358: Invalid expression
Cannot acquire a lock.
Cannot acquire a lock.
Failed to execute (SelectLayerByAttribute).
Failed at Wed Jan 15 13:00:56 2014 (Elapsed Time: 0.00 seconds)

The treatment_maps features class contains polygons and counts (DI_Count) for points located within each polygon, which need to be updated. I'm hoping to get this script to work properly as I have around 100 polygons to update.


1 Answer 1


Give this a try:

where="map_name = '%s'" % (map)

Also on your get count line, if DI_Count is an Integer field - change it to something like this:

count = int(arcpy.GetCount_management(ds).getCount(0))

I looks like you are wanting to select all the points within each treatment area and get a count and populate that treatment area with the point count? correct? If this is true, try the following:

# treatment_maps_ds - this is the name of your input polygon dataset
treatment_area_list = [row.map_name for row in arcpy.SearchCursor(treatment_maps_ds)]
# point_ds - this is the name of your input point dataset
arcpy.MakeFeatureLayer_management(point_ds, "ptslyr")
arcpy.MakeFeatureLayer_management(treatment_map_ds, "treatmentlyr")

# Loops through each treatment 'map_name'
treatdict = {}
for treatmap in treatment_area_list:
    arcpy.SelectLayerByAttribute_management("treatmentlyr", "NEW_SELECTION", "map_name = '" + str(treatmap) + "'")
    arcpy.SelectLayerByLocation_management("pntlyr", "INTERSECTS", "", "treatmentlyr")
    cnt = int(arcpy.GetCount_management("pntlyr").getOutput(0))
    treatdict[treatmap] = cnt

cur,row = None, None
cur = arcpy.UpdateCursor(treatment_maps_ds)
for row in cur:
    cnt = treatdict[row.map_name]
    row.DI_Count = cnt
  • I tried this and recieved the following error, very similar to the original one:Executing: SelectLayerByAttribute maps NEW_SELECTION "map_name = 'Airport'" Start Time: Tue Jan 21 07:48:15 2014 ERROR 000358: Invalid expression Cannot acquire a lock. Cannot acquire a lock. Failed to execute (SelectLayerByAttribute). Failed at Tue Jan 21 07:48:15 2014 (Elapsed Time: 0.00 seconds) Commented Jan 21, 2014 at 15:49
  • Not sure - that expression seems to be correct. Although it says you cannot acquire a lock - which tells me that perhaps it is locked by another program. I would suggest closing all ESRI programs before running your script.
    – dklassen
    Commented Jan 21, 2014 at 17:41
  • In my tests - on a string field, this expression works fine. What is the feature class you are quering? SDE/File GDB/ Shapefile?
    – dklassen
    Commented Jan 21, 2014 at 17:51
  • I am looking at your question again and see that the "treatment maps" which you are cursoring through and the "maps" which you are selecting by attribute on - are the same layer - this cannot be done - because you are locking the file with the cursor - and looping through. I think the data processing methodology needs to be revisited. I will edit my answer to this regard.
    – dklassen
    Commented Jan 21, 2014 at 18:12
  • You are correct and thank you for your answer. I figured out a workaround by creating a dummy shapefile with the field names (map names) I was looking for and used that as my selecting layer while keeping the cursor on the original layer. It worked perfectly but if you have any suggestions on efficiency I wouldn't mind hearing them. Thanks again. Commented Jan 22, 2014 at 15:33

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