LegendItem is added to Legend when definition query on the layer is updated

Question

I have a script to generate map outputs using an APRX with predefined layouts. In the script, I am changing definition queries on multiple layers in layout's map frame, then change extent etc. and finally export a PNG. Legend items are strictly pre-defined as well, to prevent any overlapping with map frame for example.

I use this approach:

expression = "SOME SQL QUERY"
layer.definitionQuery = expression

I haven't run the script in a while, and now when I did so (after updating the APRX a bit in Pro 3.6), the layers where definition query was changed are automatically added to Legend element (all of them if there are multiple Legends in the layout) right after the code above runs. This is not desired in my case, as I mentioned above - the legend then stretches and overlaps map frame and other elements.

I can (and did) script a workaround, but is this expected behavior? I would prefer the layers not to be automatically added there.

RomanBoros · Answer

I was not accessing the LegendElement in the code at all, since I set up the layout and legend itself completely in Pro and there was no need for me to access it in the code. Now I need to access it to remove unwanted items from it.

I checked and "syncNewLayer" is set to True indeed. But I am not adding any new layer to the map, just setting a definition query to layers which are already in the map. I don't want them to show in the legend though, which is why I don't have them there originally, they are only added there right after the code sets the "layer.definitionQuery" property (checked this in debugger).

The quick workaround I was able to come up with is storing original legend items right after the layout is loaded and then removing unwanted items added during code run before PNG export:

legend = layout.listElements(wildcard='Legend')[0]
legend_items = [a.name for a in legend.items]
...
CORE CODE RUNS
...
for item in legend.items:
  if item.name not in legend_items:
    legend.removeItem(item)
layout.exportToPNG(...)

DanPatterson · Answer

LegendElement—ArcGIS Pro | Documentation

are you accessing LegendElement within your script? there is syncNewLayer set to True somehow?

You said you have a code workaround which you might want to share