Creating a new label class in Arc Pro using the arcpy CIM

[Anonymous User]

I am attempting to create a new label class for a layer using the arcpy CIM, code below. The new label class gets created, but ArcGIS Pro immediately crashes when I attempt to interact with it in the GUI. I have tried in the python window and in a script. 

aprx = arcpy.mp.ArcGISProject('CURRENT')
m = aprx.listMaps("Map")[0]
lyr = m.listLayers("SOME LAYER")[0]
ldef = lyr.getDefinition('V2')

newlblclass = arcpy.cim.CreateCIMObjectFromClassName('CIMLabelClass','V2')
newlblclass.name = "NEW CLASS"
newlblclass.visibility = True
ldef.labelClasses.append(newlblclass)
lyr.setDefinition(ldef)

[DuncanHornby · Accepted solution]

May be there are required properties that need setting? All you set is the name and visibility, but what about the field that the label is derived from?

[Anonymous User · Accepted solution]

Correct. After researching there are many "nested" CIMobjects that make up a label class cim object. All of these objects need to be created and assigned in order for the label class object to function properly. 

Reference: https://pro.arcgis.com/en/pro-app/arcpy/mapping/python-cim-access.htm

[anyry]

Can you please share your label class creation solution? I have the same problem and I can't solve it. Thanks

[DestinyKelley1]

My solution is different, and may be of help to you if you are still experiencing this issue.   I have figured out a way to bypass the corruption of the CIM definition when attempting to create a new label class with ArcPy CIM.  To test this out, you can use any layer those default class is named "Class 1." Instead of using arcpy.cim.CreateCIMObjectFromClassName('CIMLabelClass','V2') or arcpy.cim.CIMLabelClass() as suggested by other users, I used cimObject.labelClasses.copy(). 

It's a little awkward, but I hope it helps!

The code to try out is below:

import arcpy

p = arcpy.mp.ArcGISProject('CURRENT')
m = p.listMaps('Map')[0]
layer = m.listLayers("Your Layer Name Here")[0]
cimObject = layer.getDefinition('V2')
lblClasses = cimObject.labelClasses
    
for lblClass in lblClasses:
    if lblClass.name == "Class 1":
        nlc_index = cimObject.labelClasses.index(lblClass)
        lblClass_copy = cimObject.labelClasses.copy()[nlc_index]
        cimObject.labelClasses.append(lblClass_copy)
        layer.setDefinition(cimObject)
        break

cimObject = layer.getDefinition('V2')
lblClasses = cimObject.labelClasses        
        
for lblClass in lblClasses:
    if lblClass.name == "Class 1":
        nlc_index = cimObject.labelClasses.index(lblClass)
        if nlc_index != 0:
            lblClass.name = "Dummy"
            layer.setDefinition(cimObject)

[JingchaoZhou]

Just wondering if you can change the label class name before you append it in the first for loop

something like this 

for lblClass in lblClasses:
    if lblClass.name == "Class 1":
        nlc_index = cimObject.labelClasses.index(lblClass)
        lblClass_copy = cimObject.labelClasses.copy()[nlc_index]
        
        lblClass_copy.name = "new_class_name"
        cimObject.labelClasses.append(lblClass_copy)
        layer.setDefinition(cimObject)
        break

I have not tested this, but just wondering if this will optimize the code and avoid the second for loop....