topic Re: ApplySymbologyFromLayer toolbox Python script problem in ArcGIS Pro Questions

ApplySymbologyFromLayer toolbox Python script problem

Anonymous User — Wed, 14 Dec 2022 00:27:22 GMT

arcpy.management.ApplySymbologyFromLayer() works from a standalone script, or the Arc Python window, but NOT from a toolbox script inside a map session. It executes without an error, but it doesn't change the symbology.

The only possible reason I can see is that the object type is a little different for a layer depending on whether it's a standalone/python window or the toolbox script.

standalone/python window layer type: <arcpy._mp.Layer object at 0x000001C3E7390C10>

toolbox script layer type: <MappingLayerObject object at 0x000001AEA43E2270>

Does anyone know what's going on?? I have run into other weird glitches with ArcGIS Pro where tools function differently in toolbox scripts, and it's very frustrating.

Script example that only works if run as a standalone script:

Re: ApplySymbologyFromLayer toolbox Python script problem

DanPatterson — Wed, 14 Dec 2022 00:54:26 GMT

Are you using a custom toolbox where you can specify the parameter type from a dialog or is this a parameter-less tool? A toolbox script will behave properly if you define the parameters in the tool and select them from the dialog like this?

Re: ApplySymbologyFromLayer toolbox Python script problem

Anonymous User — Wed, 14 Dec 2022 01:04:23 GMT

I was grabbing the layers through the map.listLayers() method because one of them will be an in-memory layer that I created in my script, not a user input.

But I just tried making them both user input parameters (Feature Layers), and it still didn't work.

Re: ApplySymbologyFromLayer toolbox Python script problem

JohannesLindner — Wed, 14 Dec 2022 05:59:36 GMT

From the tool doc:

To see the symbology created in a script tool, the tool must include the layer as a derived output parameter.

Re: ApplySymbologyFromLayer toolbox Python script problem

mody_buchbinder — Wed, 14 Dec 2022 06:12:26 GMT

More or less the same code works for me when I take the source layer from lyrx file and not from the TOC

Re: ApplySymbologyFromLayer toolbox Python script problem

Anonymous User — Wed, 14 Dec 2022 16:58:42 GMT

Ahh, thanks! I guess I should have read the doc more thoroughly. I've been avoiding derived parameters, because I didn't understand them.

Here's the code that works.

Re: ApplySymbologyFromLayer toolbox Python script problem

Anonymous User — Wed, 14 Dec 2022 19:05:22 GMT

Actually, I found a better solution for my purposes. I was having an issue with the derived output adding a second copy of the layer being affected, when that layer was an in-memory layer. When I changed so that it wasn't added to the map at all until the derived output from the symbology tool, then I realized that the derived output doesn't get added to the map until the script ends. This is a problem because I need to apply symbology, and then edit it within the same script.

Here's the new method that works better when your affected layer is an in-memory layer: no duplication, and immediately added to map.

I know this seems like a pointless script... it's just a fragment of a larger script.

Re: ApplySymbologyFromLayer toolbox Python script problem

MichaelPorter — Wed, 28 Feb 2024 16:25:51 GMT

This worked for me. Thanks!

Re: ApplySymbologyFromLayer toolbox Python script problem

MatthewSackrison — Fri, 20 Mar 2026 13:11:37 GMT

Thanks for posting! This fixed my issue, too, without needing to mess around with all the derived output stuff.