Understanding arcpy.mp's addLayerToGroup
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?
Don't want to edit the original post because of this forum's added-line bug.
Here's the tool side of that parameter:
