I have many layers on a map. I need to write an Arcade expression in the symbol size expression box, but I need to do it in all the layers. I do not want to do that one by one.

I wanted to create a script that add the Arcade expression for the custom symbol size on ArcGIS Pro. I have already done a script before that adds a query layer expression automatically using:

if lyr.supports("DEFINITIONQUERY"):
     lyr.definitionQuery = ...

Obviously symbol size expression is totally different but it is still an expression that I want to add to all the layers.

Is this even possible?

I haven't found anything on forums yet.

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1 Answer 1


If you want to script the setting of the symbol size using a custom expression then you need to be using the CIM module through ArcPy and you can control the ValueExpressionInfo. Take note of the cautions and I would recommend you install the CIM viewer so you can see a layers properties and then understand how to navigate the CIM properties via ArcPy.

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