I have an unanswered question about arpcy.mapping here: https://community.esri.com/message/395210?sr=search&searchId=217e8af9-1d87-4cde-a095-f520d1ef56cd&searchIndex=1#395210
The format is getting really long and messy and it hasn't been answered yet. For the history please read thru it. But I think the problem seems to be a bug with the way arcpy.mapping.listLayers works or doesn't work.
in the interactive python window using my mxd I can list layers and see my layer of interest: "Dimensions". If I perform the same command in my script, the "Dimensions" layer does not appear. yet I'm using the same commands on the same mxd.
i've used "CURRENT" and the pathname to the mxd.
please see the attached to see what I'm talking about plus the previous forum post above. Help is desperately required and much appreciated!!!