Removing layer symbology with no object using ArcPy?

Question

I have a layer named 'Landuse' in TOC. Symbology type is 'Unique value" for the field 'Landuse', for example:

• Residential
• Commercial
• Public
• Recreational
• Etc.

Is there any way to automatically remove Commercial (for example) since actually there is no 'Commercial' polygon in 'Landuse' layer by existing tool or by Arcpy coding?

Because there are many unique values in the 'Landuse' layer, and I have to do it many times, so that I dont want to do it manually.

Answer 1

Try this (untested) snippet on a layer.

if lyr.symbologyType = 'UNIQUE_VALUES':
    field = lyr.symbology.valueField
    freqTable = arcpy.Frequency_analysis(lyr.dataSource,"tempTable", field) 
    freq = arcpy.da.TableToNumPyArray(freqTable ,field).tolist()
    vals= [val[0] for val in freq]
    lyr.symbology.classValues = vals

Answer 2

Select Landuse layer.
Right click and select properties.
Select the tab Symbology.
Select Categories, then Unique values.
Then with the drop down option for value field select for "Unique value."

This should then list all your zoning types below in the box. Here you can then right-click on Commercial and select remove value(s). This should remove Commercial from the list of values shown in legend or toc.