I am using ArcMap 10.6 and I try to run a script in ArcMap in order to apply a certain definition query on all project layers that support definition queries.

# -*- coding: UTF-8 -*-
# import system modules
import arcpy
import sys
import os

script = sys.argv[0]
arcpy.AddMessage('running script =' + script)

# single run lines
mxd = arcpy.mapping.MapDocument("CURRENT")
dataFrame = arcpy.mapping.ListDataFrames(mxd)[0] #[0] for first dataframe
layerlist = arcpy.mapping.ListLayers(dataFrame)

Param = arcpy.GetParameterAsText(7) #0-6 are already reserved

# for loop
for layer in layerlist:
   if layer.supports("definitionQuery"):
         z = layer.definitionQuery ("NAME_PROJECT = %s") %(Param)
         layer.definitionQuery = z
         print("Layer does not support definition query.")

# refreshing

As you see, what the script does so far is just to check if layers support definition queries and if so to apply such a one that filters layers that have String based values in attribute field named "NAME_PROJECT". The script seems to successfully filter by afore-mentioned query but it does not show the definition query in the layer´s properties.

  • If the field NAME_PROJECT is text, then your comparison will fail because the constant isn't quoted with apostrophes.
    – Vince
    Oct 6, 2022 at 16:33
  • ListLayers (mxd) is a way to go.
    – FelixIP
    Oct 7, 2022 at 4:07

1 Answer 1


You have a test already to see if def query is supported so you are not testing for this in the try/except, you are catching a failure. It is possibly an error in the line

z = layer.definitionQuery ("NAME_PROJECT = %s") %(Param)

Attempt the below.

# for loop, iterate through the layers
for layer in layerlist:
   # print the layer name so you can see if success or fail
   # check if the layer supports def query and if it does
   if layer.supports("definitionQuery"):
      # try add a def query
         z = "NAME_PROJECT = '{0}'".format(Param)
         layer.definitionQuery = z
      # if it fails to add a def query then say so
         arcpy.AddMessage("Failed to apply def query")
   # if def query is not supported then say so       
         arcpy.AddMessage("Layer does not support definition query.")

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