Wednesday, 20 December 2017

ArcPy - MoveLayer fails with "assert refe_c is not None, 'Did not find reference layer.'"

Just wanted to copy and paste all layers into new MXD file. Unfortunately order of layers in TOC is not retained. So I googled for script and found one - but MoveLayer failed with error message "assert refe_c is not None, 'Did not find reference layer.'". The post did not mention anything like that.

Solution in my case : for the reference layer a fresh reference is required. 

old: refLayer=moveLayer
new: refLayer = arcpy.mapping.ListLayers(mxdT,, dfT)[0]  

ArcMap 10.3.1

Here is the script:

 # -*- coding: utf-8 -*-  
 # source code initially taken from:  
 # assumption : no layer groups  
 # my use case : copy and paste all layers into new MXD, layer order is not retained - run script to restore layer order  
 import arcpy  
 mxd_source = r"C:\temp\source1.mxd"  
 mxd_target = r"C:\temp\target.mxd"  
 mxdT = arcpy.mapping.MapDocument(mxd_target)  
 # assumption: only one DF  
 dfT = arcpy.mapping.ListDataFrames(mxdT, "")[0]  
 mxdS = arcpy.mapping.MapDocument(mxd_source)  
 # assumption: only one DF  
 dfS = arcpy.mapping.ListDataFrames(mxdS, "")[0]  
 #initialize refLayer with layer  
 refLayer = arcpy.mapping.ListLayers(mxdT,"",dfT)[0]  
 for layerSource in arcpy.mapping.ListLayers(mxdS,"",dfS):    
   print("processing layer in source: '" + sourceLayer+"'.")    
   for layerTarget in arcpy.mapping.ListLayers(mxdT,"",dfT):  
    moveLayer= a+b     
    if sourceLayer==moveLayer:  
      print("moving layer:'"+moveLayer+"', reference layer: '""'.")  
      arcpy.mapping.MoveLayer(dfT,refLayer,moveLayer, "After")       
      #get fresh layer reference - otherwise MoveLayer will fail next time:  
      refLayer = arcpy.mapping.ListLayers(mxdT,, dfT)[0]             

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