Setting transparency for all layers in a data frame in ArcMap using ArcPy?

Question

Using ArcMap 10.6, I've tried the following code from a previous post and get an error or it executes but does nothing. Here is the code and error I receive:

Code

mxd = arcpy.mapping.MapDocument ("CURRENT")
df = arcpy.mapping.ListDataFrames (mxd, "Layers") [0]
for lyr in arcpy.mapping.ListLayers (mxd,"", df):
 lyr.transparency = 0
arcpy.RefreshActiveView()
mxd.save
del mxd

Error

RuntimeError: LayerObject: Set attribute transparency does not exist

• Michael Stimson: Try testing if the layer supports transparency first resources.arcgis.com/en/help/main/10.2/index.html#/Layer/… if lyr.supports (layer_property): lyr.transparency = 0. Or the crash and burn approach try: lyr.transparency = 0 except: pass
• PolyGeo: Try printing lyr.name before trying to change its transparency to see which layer gives you the error. Also, please always provide the full error message including its line number. When refering to any previous post please always include a link to it.

Answer 1

As was mentioned by @Michael Stimson, not all layers support transparency.

From the documentation:

Not all layers support the transparency property (for example, fabric group layers and web service sublayers), so it is good practice to test for this ahead of time using the supports method.

So, your code could look like this:

mxd = arcpy.mapping.MapDocument ("CURRENT")
df = arcpy.mapping.ListDataFrames (mxd, "Layers") [0]
for lyr in arcpy.mapping.ListLayers (mxd,"", df):
 if lyr.supports("TRANSPARENCY"):
 lyr.transparency = 0
arcpy.RefreshActiveView()
mxd.save
del mxd

One other thing to check is that your data frame is actually called "Layers". If not, the code won't do anything.

It's also important to know that 0 means the layer is not transparent, but 100 means the layer is completely transparent.