Why does this python tool script add output layer twice?

[ThomasMiller24]

Hello, I'm trying to change the symbology of a feature class (symbology is unique values based on a field within the attribute) and add some definition queries. However, whenever I run the tool, it adds two duplicate output layers to the model.

I include a snippet of code below. I presume this is because I use addDataFromPath and SetParameter. But I don't see how I can avoid using these, since the tool requires SetParameter and to access the symbology I need to create a layer. 

In which case, how do I prevent the layer being added twice?

• m.removeLayer(lyr) removes both layers
• This occurs regardless whether Add Outputs to Map is switched off or not in the aprx (env setting shouldn't (and doesn't) work in a python script)
• I have tried using a lyrx file for the symbology but the definition queries are not transferred

Any thoughts what I might be missing?

Many thanks in advance

Tom

import arcpy

input_fc = "File path to input feature class"
polygon_symbology = "Some Symbology Dict"
definition_query = "Set of Definition Queries"
field = "field name"

m = arcpy.mp.ArcGISProject("CURRENT").activeMap
lyr = m.addDataFromPath(input_fc)
sym = lyr.symbology
sym.updateRenderer('UniqueValueRenderer')
sym.renderer.fields = [field]
for grp in sym.renderer.groups:
    for itm in grp.items:
        myVal = itm.values[0][0]
        arcpy.AddMessage(f"Applying symbology for {myVal}")
        if myVal in polygon_symbology:
            symbology_list = polygon_symbology[myVal]
            arcpy.AddMessage(f"Applying symbology: {symbology_list}")
            itm.symbol.applySymbolFromGallery(symbology_list[0])
            itm.symbol.size = symbology_list[1]
            itm.symbol.outlineColor = symbology_list[2]
        else:
            arcpy.AddMessage(f"Warning: {myVal} not found in descriptions. Skipping symbology assignment.")
lyr.symbology = sym
lyr.updateDefinitionQueries(definition_query)

arcpy.SetParameter(1, lyr)
arcpy.mp.ArcGISProject("CURRENT").save()
del m

[AlfredBaldenweck]

So, it looks like it's that SetParameter() that's causing the extra layer to be added. Is there a workflow need for it that we're not seeing here?

Basically I copied your code and commented out the SetParameter and things worked just fine for me.

[ThomasMiller24]

Thanks for the reply. However, my understanding is that SetParameter needs to be included to make the connection permanent otherwise the result layer is lost. Or am I misunderstanding something? 

I perhaps should mention that the input_fc is actually an output from the geoprocessing tool.

[AlfredBaldenweck]

I don't have many workflows involving adding a layer to my map, but to be honest I've never once used SetParameter() for the ones that do. I'd just try taking it out and seeing if it works. The important stuff that you're doing to the layer doesn't depend on it.