Strange Python vs Arcade symbology issue

Question

For the TWP+"_Sections" layer I have to set the lblClass.expression with python, for the TWP+"_QRT_sections" layer I have to set it with Arcade, otherwise neither layer works! It's the strangest thing. The problem repeats with each new dataset. Here's the code in question: for m in aprx.listMaps("Map"): for lyr in m.listLayers(TWP+"_Sections"): sym = lyr.symbology lblClass = lyr.listLabelClasses()[0] print("Layer name: " + lyr.name) lblClass.expression = "\"\" + \"\" + [FRSTDIVNO] + \"\" + \"\"" #lblClass.expression = "\"\" + \"\" + $feature.FRSTDIVNO + \"\" + \"\"" lyr.showLabels = True sym.renderer.symbol.color = {'RGB' : [0, 0, 0, 0]} sym.renderer.symbol.outlineColor = {'RGB' : [0, 38, 138, 100]} sym.renderer.symbol.outlineWidth = 4 lyr.symbology = sym p.saveACopy(os.path.join("CURRENT")) for lyr in m.listLayers(TWP+"_QRT_sections"): sym = lyr.symbology lblClass = lyr.listLabelClasses()[0] print("Layer name: " + lyr.name) #lblClass.expression = "\"\" + \"\" + [SECDIVNO] + \"\" + \"\"" lblClass.expression = "\"\" + \"\" + $feature.SECDIVNO + \"\" + \"\"" lyr.showLabels = True sym.renderer.symbol.color = {'RGB' : [0, 0, 0, 0]} sym.renderer.symbol.outlineColor = {'RGB' : [171, 205, 102, 100]} sym.renderer.symbol.outlineWidth = 4 lyr.symbology = sym p.saveACopy(os.path.join("CURRENT")) Any ideas?

danieloccasionally · Answer

Thank you @RhettZufelt and @JohannesLindner . It's always something simple!

JohannesLindner · Answer

That's probably it. To set the expression engine, you have to use the CIM:

for lyr in m.listLayers(TWP+"_Sections"):
        cim = lyr.getDefinition("V3")
        for lblClass in cim.labelClasses:
            lblClass.expressionEngine = "Arcade"
        lyr.setDefinition(cim)
        # rest of the code

rzufelt · Answer

Any chance the label class(es) for TWP+"_QRT_sections" in the map are set to arcade language and the other to Python?

R_