Understanding arcpy.mp's addLayerToGroup

MErikReedAugusta — Tue, 16 Apr 2024 13:56:40 GMT

So, I'm genuinely confused by this.

I have a python script tool that needs to go find a SID file in our directory, pull it into the map, and add it to an already-existing Group Layer.

The Group Layer is provided to the tool by the user.

Simplified code below:

aprx = arcpy.mp.ArcGISProject('CURRENT') mxd = aprx.activeMap recordLayerGrp = arcpy.GetParameter(7) # Note that I'm not pulling as Text; # this comes through as an # arcpy.mp.Layer object # [... intermediate code where I work with this and other layer objects just fine...] mxd.addLayerToGroup(recordLayerGrp, # At the point the function gets this # variable, it's unchanged from input; # I pass it directly from the input # function to this function. fileLayerObj, # This is also an arcpy.mp.Layer object 'TOP', )

This consistently fails with a ValueError. After a bunch of headache, I managed to determine that said error is referencing the arcpy.mp.Layer object behind recordLayerGrp.

I went and did quite a bit of spelunking on this issue yesterday and today, and finally added a single line to the code (line 2, below):

recordLayerGrp = arcpy.GetParameter(7) recordLayerGrp = [lyr for lyr in mxd.listLayers() if lyr.name == recordLayerGrp.name][0]

The result of this is still an arcpy.mp.Layer object, but it's a different instance. And this different one suddenly magically works. I even added debug statements before and after line 2, to see what was in recordLayerGrp at each step:

The tool inputs directly ask for the Group Layer and the user selects it. Why did I have to "convert" the arcpy.mp.Layer object and go look for that Group Layer again? Why doesn't the tool pull the "correct" instance of that object?

Re: Understanding arcpy.mp's addLayerToGroup

MErikReedAugusta — Tue, 16 Apr 2024 13:58:36 GMT

Don't want to edit the original post because of this forum's added-line bug.

Here's the tool side of that parameter:

Re: Understanding arcpy.mp's addLayerToGroup

BlakeTerhune — Tue, 16 Apr 2024 14:12:12 GMT

Your mxd variable name is messing with me! What version of Pro are you using?

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Understanding arcpy.mp's addLayerToGroup

Re: Understanding arcpy.mp's addLayerToGroup

Re: Understanding arcpy.mp's addLayerToGroup