Customize the legend through ArcPy.

gauravparajuli9

Hi everyone,

I’m working on a project where I need to automate map production in ArcGIS Pro using ArcPy. One of the layers in my layout is the USA Cropland dataset, which contains nearly 150 cropland classes. Including all of these classes in the legend makes the map extremely cluttered.

What I would like to do is display only the top 10 classes for each state, based on pixel count, and group the remaining classes into an “Other Classes” category.

Is there a way to achieve this dynamically using ArcPy—either by modifying the legend, the symbology, or by generating a temporary raster/layer for each state?

Any guidance or examples would be greatly appreciated.

Thank you!

Clubdebambos

Hi @gauravparajuli9,

If you are changing symbology to only show the top 10, all other values will be the same color. If that is ok, you can use the Python CIM with ArcPy. Create the symbology for all cropland classes and add the option to Include all other values. Save as a layer file. 

 

While I have not fully tried the following, it is a guide for the workflow (that may work first time around 😅)

## access the APRX. You can set to be the APRX path
aprx = arcpy.mp.ArcGISProject("CURRENT")

## get the layout
lyt = aprx.listMaps("LAYOUT_NAME")[0]
m = lyt.listEelements("MAPFRAME_ELEMENT", "MF_NAME")[0].map
rst_lyr = m.listLayers("RASTER_LAYER_NAME")[0]

## apply the symbology
arcpy.management.ApplySymbologyFromLayer(rst_lyr, "PATH_TO_LYRX")

## get top 10
# Raster attribute table already has a count
count_dict = {row[0] : row[1] for row in arcpy.da.SearchCursor(rst_lyr, ["YOUR_CODE_FIELD_HERE", "Count"])}

# top 10 codes
top_10 = [
    code for code, count in sorted(
        count_dict.items(),
        key=lambda x: x[1],
        reverse=True
    )[:10]
]

## get CIM definition
cim = rst_lyr.getDefinition('V3')

## remove any codes that are not it top 10 - they go into other
cim.colorizer.groups[0].classes = [item for item in cim.colorizer.groups[0].classes if item.values[0] in top_10]

## update the CIM def for the layer
rst_lyr.setDefinition(cim)

## EXPORT ##