ApplySymbologyFromLayer toolbox Python script problem

[Anonymous User]

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:

[DanPatterson]

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?

[Anonymous User]

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.

[JohannesLindner · Accepted solution]

From the tool doc:

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

[Anonymous User]

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.

 

 

[Anonymous User]

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.

 

 

[MichaelPorter]

This worked for me. Thanks!

[MatthewSackrison]

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

[mody_buchbinder]

Hi

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