LabelClass

Summary

Provides access to a layer's label class properties.

Discussion

The LabelClass object is used for managing labeling properties such as label expressions or SQL queries that are associated with a layer's individual label classes. The listLabelClasses method on the Layer object will return a list of existing LabelClass objects. The createLabelClass method on the Layer object returns a reference to a new LabelClass.

Not all layers support labeling, so it is useful to test this ahead of time using the supports method on the Layer object. For example:

if lyr.supports("SHOWLABELS"):

If this statement is True, you will be able to modify all label class properties.

Properties

Property	Explanation	Data Type
expression (Read and Write)	A layer's individual label class expression using either a VBScript, JScript, or Python parser associated with the label class.	String
name (Read and Write)	A layer's individual label class name.	String
SQLQuery (Read and Write)	A layer's individual label class SQLQuery. This is useful for restricting labels to certain features.	String
visible (Read and Write)	If True, the label class is visible. If False, it is not visible.	Boolean

Method Overview

Method	Explanation
getDefinition (cim_version)	Returns a label classes' CIM definition.
setDefinition (definition_object)	Sets a label classes' CIM definition.

Methods

getDefinition (cim_version)

Parameter	Explanation	Data Type
cim_version	A string that represents the major version of the CIM that will be used. V2—The 2.x version of the CIM will be used. V3—The 3.x version of the CIM will be used.	String

Return Value

Data Type	Explanation
Object	Returns the CIM definition for a LabelClass.

For more information about working with the CIM and samples, see Python CIM access.

setDefinition (definition_object)

Parameter	Explanation	Data Type
definition_object	A modified CIM definition object originally retrieved using getDefinition.	Object

For more information about working with the CIM and samples, see Python CIM access.

Code sample

LabelClass example 1

The following script will print the label class properties for only those layers that have labels turned on and supports the showLabels property.

import arcpy
aprx = arcpy.mp.ArcGISProject(r"C:\Projects\YosemiteNP\Yosemite.aprx")
m = aprx.listMaps("Yosemite National Park")[0]

for lyr in m.listLayers():
    if lyr.supports("SHOWLABELS"):
        if lyr.showLabels:
            print("Layer name: " + lyr.name)
            for lblClass in lyr.listLabelClasses():
                print("\t Class Name: \t" + lblClass.name)
                print("\t Expression: \t" + lblClass.expression)
                print("\t SQL Query:  \t" + lblClass.SQLQuery)
del aprx

LabelClass example 2

The following script finds a layer named Points of Interest and changes the label class properties for a particular label class named Summit so that not all of the summits are labeled. Only those over 2,000 meters in elevation are labeled.

import arcpy
aprx = arcpy.mp.ArcGISProject(r"C:\Projects\YosemiteNP\Yosemite.aprx")
m = aprx.listMaps("Yosemite National Park")[0]

lyr = m.listLayers("Points of Interest")[0]

if lyr.supports("SHOWLABELS"):
  lblClass = lyr.listLabelClasses("Summit")[0]
  lblClass.expression = "Name"
  lblClass.SQLQuery = "Type_ = 'summit' And Elevation > 2000"
  lblClass.visible = True

aprx.save()
del aprx

LabelClass example 3

The following script creates two new label classes using Python and Arcade language options.

p = arcpy.mp.ArcGISProject('current')
m = p.listMaps('Map')[0]
l = m.listLayers('GreatLakes')[0]

#Enable layer labels but toggle off all existing label classes
l.showLabels = True
for lc in l.listLabelClasses():
    lc.visible = False

#Create new Label classes and toggle those on
lc1 = l.createLabelClass(name = 'Small Lakes - Python',
                         expression = '[AREA]',
                         sql_query = 'AREA < 10000',
                         labelclass_language = 'Python')
lc1.visible = True

lc2 = l.createLabelClass(name = 'Large Lakes - Arcade',
                         expression = '$feature.AREA',
                         sql_query = 'AREA > 10000',
                         labelclass_language = 'Arcade')
lc2.visible = True