Layer

Summary

Provides access to basic layer properties and methods.

Discussion

Layers can be referenced from within a project using the listLayers method on the Map class or in a layer file (.lyr or .lyrx) stored on disk using the listLayers method on the LayerFile class.

The Layer object has a single, generic design to work with all layers. There are numerous types of layers, and not all of them support the same set of properties. For example, a feature layer supports a definition query, whereas a raster layer does not, but a raster catalog does. Rather than having to work with different, individual layer objects for all the possible layer types and property combinations, there are some useful properties that allow you to obtain information about a layer and its supported properties. There are many is properties that allow you to determine if a layer fits into a general category, for example, is3DLayer, isFeatureLayer, isGroupLayer, isRasterLayer, isWebLayer, and so on.

There are a few specialized layers and datasets that don't fall into one of these general categories: annotation subclasses, dimension features, terrain datasets, topology datasets, and so on. In these cases, you may need to test other properties to isolate a layer of interest before doing something to it. The supports method is available to help identify which specific layer supports which specific layer property. It gives you the ability to test whether the layer supports a property before trying to get or set its value, reducing the need for additional error trapping. For example, see the following code:

if lyr.supports("BRIGHTNESS"):
    lyr.brightness = 10

The listLayers method on the Map class returns index values that are generated from top to bottom as they appear in the table of contents or as they appear in a layer file. The same applies if a group layer is within another group layer. For example, a map with a single group layer that contains three sublayers will return a list of four layer names, the group layer being the first and the three sublayers being the second, third, and fourth. There are two ways of determining if a layer is a group layer. First, you can check to see if the layer supports the isGroupLayer property. Second, you can evaluate the longName property. A layer's longName value will include the group name in addition to the layer name. For example, a layer named Layer1 in a group layer named Group1 will have a longName value of Group1\Layer1. If the name value is equal to the longName value, the layer is not inside a group layer. When working with the sublayers of composite layers, the longName property will contain both the sublayer and top-level layer name.

ArcGIS Pro can read legacy .lyr file types, but it can only save to .lyrx file types. If a .lyr file type is being referenced and the save method is called, it will be converted to a .lyrx file type but with the same file name.

A feature layer can support zero to many definition queries, but only one definition query can be active. It is also possible that one or many definition queries are present but none are active. There are a couple of ways to manage definition queries. First, you can use the definitionQuery property. If you set a unique SQL string on a layer that does not have a definition query or a layer that has multiple definition queries, the new definition query is added and it becomes the active query. If you set a SQL string on a layer that already has that same query, it sets that as the active definition query, if it is not already active. The second way to manage definition queries is to use the listDefinitionQueries and updateDefinitionQueries functions in combination. The listDefinitionQueries function returns a list of Python dictionaries that represent the properties associated with each query. The dictionary keys are name, sql, and isActive. Definition queries can be added, modified, or removed from the Python list using core Python. The dictionary isActive value can be set to True to set the active query. Again, only one query can be active. If you try setting more than one query to be active, an error will be returned. After changes are made, the updateDefinitionQueries function is used to set the new changes.

Changing a layer's data source is a common requirement. There is a method and a property on the Layer object that help with this. For a more detailed discussion, parameter information, scenarios, and code samples, refer to the Updating and fixing data sources help topic.

Properties

Property	Explanation	Data Type
brightness (Read and Write)	A layer's brightness value. The default, normal brightness, is 0 percent. Enter any value between +100 percent and -100 percent. Type a plus or minus sign to the left of the value to specify whether it is above or below 0.	Integer
connectionProperties (Read Only)	Returns a layer's data source connection information as a Python dictionary.	Dictionary
contrast (Read and Write)	A layer's contrast value. The default, neutral contrast, is 0 percent. Enter any value between +100 percent and -100 percent. Type a plus or minus sign to the left of the value to specify whether it is above or below 0.	Integer
dataSource (Read Only)	Returns the complete path for the layer's data source. It includes the full workspace path and name of the dataset. For enterprise geodatabase layers, a string containing the layer's connection information is returned. Tip: Enterprise geodatabase layers in an ArcGIS Pro project do not retain the path to the database connection file (.sde) that was used to create the layer.	String
definitionQuery (Read and Write)	A layer's definition query. If you set a unique SQL string on a layer that does not have a definition query or a layer that has multiple definition queries, the new definition query is added and it becomes the active query. If you set a SQL string on a layer that already has that same query, it simply sets that as the active definition query, if it is not already active.	String
is3DLayer (Read Only)	Returns True if a layer is a 3D layer.	Boolean
isBasemapLayer (Read Only)	Returns True if a layer is a basemap layer.	Boolean
isBroken (Read Only)	Returns True if a layer's data source is broken.	Boolean
isFeatureLayer (Read Only)	Returns True if a layer is a feature layer.	Boolean
isGroupLayer (Read Only)	Returns True if a layer is a group layer.	Boolean
isNetworkAnalystLayer (Read Only)	Returns True if a layer is an ArcGIS Network Analyst extension layer.	Boolean
isNetworkDatasetLayer (Read Only)	Returns True if a layer is an ArcGIS Network Analyst extension network dataset layer.	Boolean
isRasterLayer (Read Only)	Returns True if a layer is a raster layer.	Boolean
isSceneLayer (Read Only)	Returns True if a layer is a scene layer.	Boolean
isTimeEnabled (Read Only)	Indicates whether time is enabled on the layer. If isTimeEnabled returns True, the time property on the layer can be used to return a LayerTime object. Use the enableTime method to enable time on a layer that contains time information.	Boolean
isWebLayer (Read Only)	Returns True if a layer is a GIS service layer. GIS services are automated geographic information services that are published and accessed over the web using standard technologies and protocols. Esri basemaps are an example.	Boolean
longName (Read Only)	A layer's full name including group layer and composite layer structure.	String
maxThreshold (Read and Write)	A layer's maximum scale threshold for 2D maps and its maximum distance above ground for 3D maps. A layer will not display when zoomed in beyond the maximum scale. To clear the maximum scale, set the value to 0.	Double
metadata (Read and Write)	Get or set the layer's Metadata class information. Note: Setting metadata is dependent on the isReadOnly property value.	Metadata
minThreshold (Read and Write)	A layer's minimum scale threshold for 2D maps and its maximum distance above ground for 3D maps. A layer will not display when zoomed out beyond the minimum scale. To clear the minimum scale, set the value to 0.	Double
name (Read and Write)	The name of a layer the way it would appear in the table of contents. Spaces can be included. It is important that all layers in a map have a unique name so they can be easily referenced by their names.	String
showLabels (Read and Write)	Controls the display of labels for a layer. If set to True, labels will display; if set to False, labels will not be drawn.	Boolean
symbology (Read and Write)	Provides access to a layer's symbology.	Object
time (Read Only)	Returns a LayerTime object if time is enabled on the layer.	LayerTime
transparency (Read and Write)	A layer's transparency value. This enables you to see through a layer. Use values between 0 and 100. A value of 0 is not transparent. A transparency value of more than 90 percent usually results in the layer not being drawn at all.	Integer
URI (Read Only)	The Universal Resource Indicator for a layer. It is a unique identifier for a layer in a project and is sometimes required when using Python CIM access. Once a layer is added and the URI is established, the value does not change over time. For example, if you modify the layer's name, the URI will not change.	String
visible (Read and Write)	Controls the display of a layer. If set to True, the layer will draw; if set to False, the layer will not be drawn.	Boolean

Method Overview

Method	Explanation
enableTime ({startTimeField}, {endTimeField}, {autoCalculateTimeRange}, {timeDimension})	Enables time on a layer if it has time information.
extrusion ({extrusion_type}, {expression})	Extrudes 2D features in a layer to display 3D symbology.
getDefinition (cim_version)	Gets a layer's CIM definition.
getSelectionSet ()	Returns a layer's selection as a Python set of object IDs.
listDefinitionQueries ({wildcard})	Returns a Python list of definition queries associated with a layer.
listLabelClasses ({wildcard})	Returns a Python list of LabelClass objects in a layer.
listLayers ({wildcard})	Returns a Python list of Layer objects from a group layer or composite layer.
listTables ({wildcard})	Returns a Python list of Table objects that exist within a group layer.
saveACopy (file_name)	Saves a layer to a layer file (.lyrx).
setDefinition (definition_object)	Sets a layer's CIM definition.
setSelectionSet ({oidList}, {method})	Sets a layer's selection using a Python list of Object IDs.
supports (layer_property)	Used to determine if a particular layer type supports a property on the layer object. Not all layers support the same set of properties; the supports property can be used to test if a layer supports that property before attempting to set it.
updateConnectionProperties (current_connection_info, new_connection_info, {auto_update_joins_and_relates}, {validate}, {ignore_case})	Replaces connection properties using a dictionary or a path to a workspace.
updateDefinitionQueries (definitionQueries)	Updates a layer's collection of definition queries.
updateLayerFromJSON (json_data)	Updates a Layer from a JSON string.

Methods

enableTime ({startTimeField}, {endTimeField}, {autoCalculateTimeRange}, {timeDimension})

Parameter	Explanation	Data Type
startTimeField	The name of the field containing the start time values. If each feature has a single time field, specify that field name in the startTimeField and leave endTimeField blank. If each feature has a start and end time field, specify both the startTimeField and endTimeField. (The default value is None)	String
endTimeField	The name of the field containing the end time values. Not all layers use an end time field. If each feature has a single time field, specify that field name in the startTimeField and leave endTimeField blank. If each feature has a start and end time field, specify both the startTimeField and endTimeField. (The default value is None)	String
autoCalculateTimeRange	If set to True, the start and end time attribute information is used to calculate the layer's time extent. (The default value is True)	Boolean
timeDimension	The name of the dimension containing time values when using netCDF data. (The default value is None)	String

All parameters on the enableTime method are optional. If startTimeField and endTimeField are not specified, the method will evaluate the data and attempt to come up with appropriate default values.

After running the enableTime method, the time property on the layer can be used to return a LayerTime object. If a MapFrame on a Layout contains time-enabled layers, the MapTime class can be used to access map time settings.

extrusion ({extrusion_type}, {expression})

Parameter	Explanation	Data Type
extrusion_type	A string that specifies the extrusion method. The default value is NONE which turns off layer extrusion. ABSOLUTE_HEIGHT—The feature is extruded to the specified z-value, as a flat top, regardless of the z-values of the feature. BASE_HEIGHT—A z-value is calculated for each vertex of the feature's base, and the feature is extruded to the various z-values creating a multifaceted top. MAX_HEIGHT—Adds extrusion height to the minimum z-value of the feature, and the feature is extruded to a flat top at that value. MIN_HEIGHT—Adds extrusion height to the minimum z-value of the feature, and the feature is extruded to a flat top at that value. NONE—Features are not extruded. (The default value is NONE)	String
expression	A string that defines the extrusion expression, which provides an absolute extrusion height for each feature. (The default value is None)	String

Extrusion is the process of vertically stretching a flat 2D shape to create a 3D object. This provides a method to create three-dimensional symbology from two-dimensional features. Polygon and line features have all five extrusion_type options available; point features don't use MAX_HEIGHT or MIN_HEIGHT options.

getDefinition (cim_version)

Parameter	Explanation	Data Type
cim_version	A string that represents the major version of the CIM.	String

CIM-level access to additional object properties was introduced at version 2.4. Esri follows the semantic versioning specification. This means that until the next major release—for example, 3.0—when breaking API changes are allowed, the value to be used with cim_version is V2. Once 3.0 is released, a new V3 option will become available. This gives Python script authors control over the CIM version that will be used during execution if there is a possibility that breaking changes may be introduced in the new version.

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

getSelectionSet ()

Provides an easy way to retrieve the layer's current selection.

listDefinitionQueries ({wildcard})

Parameter	Explanation	Data Type
wildcard	A wildcard is based on the query name and is not case sensitive. A combination of asterisks (*) and characters can be used to limit the resulting list. (The default value is None)	String

Return Value

Data Type	Explanation
List	A Python list of dictionaries that represent the properties associated with each query. The dictionary keys are name, sql, and isActive.

Definition queries can be added, modified, or removed from the Python list using standard practices. The dictionary isActive value can be set to True to set the active query. Again, only one query can be active. If you try setting more than one query to be active, an error will be returned. After changes are made, the updateDefinitionQueries function is used to set the new changes.

listLabelClasses ({wildcard})

Parameter	Explanation	Data Type
wildcard	A wildcard is based on the label class name and is not case sensitive. A combination of asterisks (*) and characters can be used to help limit the resulting list. (The default value is None)	String

Return Value

Data Type	Explanation
List	Returns a Python list of LabelClass objects in a layer.

Returns a Python list of LabelClass objects in a layer.

listLayers ({wildcard})

Parameter	Explanation	Data Type
wildcard	A wildcard is based on the layer name and is not case sensitive. A combination of asterisks (*) and characters can be used to help limit the resulting list. (The default value is None)	String

Return Value

Data Type	Explanation
List	Returns a Python list of Layer objects from a group layer or composite layer.

Returns a Python list of Layer objects from a group layer or composite layer.

listTables ({wildcard})

Parameter	Explanation	Data Type
wildcard	A wildcard is based on the table name and is not case sensitive. A combination of asterisks (*) and characters can be used to limit the resulting list. (The default value is None)	String

Return Value

Data Type	Explanation
List	A Python list of Table objects in a layer.

Returns a Python list of Table objects that exist within a group layer. ListTables always returns a list object even if only one table is returned.

It is possible that there may be tables in a group layer with the same name. If this is the case, other properties may need to be used to isolate a specific layer. Properties such as a tables's datasource or definitionQuery or URI can be used to do this. It is ideal that all tables be uniquely named.

saveACopy (file_name)

Parameter	Explanation	Data Type
file_name	A string that includes the location and name of the output layer file (.lyrx).	String

If a group layer is being saved, all of the layers below it in the TOC will also be saved to the layer file (.lyrx).

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.

setSelectionSet ({oidList}, {method})

Parameter	Explanation	Data Type
oidList [oidList,...]	A Python list of Object IDs to use along with the appropriate selection method. (The default value is None)	Integer
method	A string that specifies which selection method to use. NEW—Creates a new feature selection from the oidList. DIFFERENCE—Selects the features that are not in the current selection but are in the oidList. INTERSECT—Selects the features that are in the current selection and the oidList. SYMDIFFERENCE—Selects the features that are in the current selection or the oidList but not both. UNION—Selects all the features in both the current selection and those in the oidList. (The default value is NEW)	String

This method provides an easy way to manage a layer's selection. To clear the selection, use the NEW selection method with an empty list or don't set any parameters.

Note: Python Lists are used for setting the oidList but Python Sets get returned from the getSelectionSet method on the Layer object.

supports (layer_property)

Parameter	Explanation	Data Type
layer_property	The name of a particular layer property that will be tested. BRIGHTNESS—A raster layer's brightness value. CONNECTIONPROPERTIES—A Layer's connection information. CONTRAST—A raster layer's contrast value DATASOURCE—A layer's file path or connection file. DEFINITIONQUERY—A layer's definition query string. LONGNAME—A layer's path including the group layers it may be nested within. MAXTHRESHOLD—A layer's maximum threshold to display the features. METADATA—A layer that can persist metadata. MINTHRESHOLD—A layer's minimum threshold to display the features. NAME—A layer's name. SHOWLABELS—A layer that can display labels. SYMBOLOGY—A layer that symbology can be accessed. TIME—A layer's time properties. TRANSPARENCY—A layer's transparency value. URI—A layer's Universal Resource Identifier. VISIBLE—A layer's visibility state. (The default value is name)	String

Return Value

Data Type	Explanation
Boolean

There are numerous types of layers and not all of them support the same properties. For example, a feature layer supports a definition query, whereas a raster layer does not, but a raster catalog does. Rather than creating individual layer objects for all possible layer types and property combinations, a supports method was created to help identify which layer types support which properties. The support method gives you the option of testing the property before trying to get or set its value on a layer type that doesn't support it. The supports property will return a True if a layer supports that property.

Boolean properties don't need to be tested using supports because if a layer property isn't supported for that layer type, a False value gets returned.

updateConnectionProperties (current_connection_info, new_connection_info, {auto_update_joins_and_relates}, {validate}, {ignore_case})

Parameter	Explanation	Data Type
current_connection_info	A string that represents the workspace path or a Python dictionary that contains connection properties to the source you want to update.	String
new_connection_info	A string that represents the workspace path or a Python dictionary that contains connection properties with the new source information.	String
auto_update_joins_and_relates	If set to True, the updateConnectionProperties method will also update the connections for associated joins or relates. (The default value is True)	Boolean
validate	If set to True, the connection properties will only be updated if the new_connection_info value is a valid connection. If it is not valid, the connection will not be replaced. If set to False, the method will set all connections to match the new_connection_info, regardless of a valid match. In this case, if a match does not exist, then the data sources would be broken. (The default value is True)	Boolean
ignore_case	Determines whether searches will be case sensitive or not. By default, queries are case sensitive. To perform case-insensitive queries, set ignore_case to True. (The default value is False)	Boolean

For more detailed discussion, parameter information, scenarios, and code samples, refer to the Updating and fixing data sources help topic.

updateDefinitionQueries (definitionQueries)

Parameter	Explanation	Data Type
definitionQueries [definitionQueries,...]	Updates a list of dictionaries that represent the properties of each definition query.	List

This function is typically used to apply the changes that have been made to the results returned by the listDefinitionQueries function.

updateLayerFromJSON (json_data)

Parameter	Explanation	Data Type
json_data	The layer definition in JavaScript Object Notation (JSON) format. See the ExportWebMap JSON specification for more information. ArcGIS API for JavaScript and ArcGIS Web AppBuilder allow you to get this JSON string from the web app. The layer definition is a subset of the webmap_json used in the ConvertWebMapToArcGISProject function. You don't need to create the web map JSON; the APIs take care of it for you. However, you need to extract the layer definition from the full webmap_json.	String

This function is intended to be used in a web tool that uses the ConvertWebMapToArcGISProject function in web map printing applications that support changing the renderer (or other properties) of dynamic web service layers. If your web tool replaces the service layers with staged vector layers after running ConvertWebMapToArcGISProject, updateLayerFromJSON will apply the renderer (or other layer properties) as specified in the webmap_json to the corresponding vector layers staged in the layout template. For more information and a code sample, see ConvertWebMapToArcGISProject.

Code sample

Layer example 1

The following script prints the name of each map in a project and lists the names of the layers in each map. The script also appends a (BROKEN) prefix to the layer name if it has a broken data source.

import arcpy
aprx = arcpy.mp.ArcGISProject(r"C:\Projects\YosemiteNP\Yosemite.aprx")
for m in aprx.listMaps():
    print("Map: {0} Layers".format(m.name))
    for lyr in m.listLayers():
        if lyr.isBroken:
            print("(BROKEN) " + lyr.name)
        else:
            print("  " + lyr.name)
del aprx

Layer example 2

The following script clears all layer definition queries and turns off labels for all layers in a map named Yosemite National Park:

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("DEFINITIONQUERY"):
        lyr.definitionQuery = ""
    if lyr.supports("SHOWLABELS"):
        lyr.showLabels = False
aprx.save()
del aprx

Layer example 3

The following script adds a new definition query to a layer or sets the same query to be the active definition query if the SQL string already exists:

p = arcpy.mp.ArcGISProject('current')
m = p.listMaps()[0]
l = m.listLayers()[0]
if l.supports('DefinitionQuery'):
  l.definitionQuery = "AREA > 3000000"

Layer example 4

The following script creates a new definition query by appending a Python dictionary to the existing list queries. Because a query may already be active, it is important to first clear existing active queries before setting the new active query.

p = arcpy.mp.ArcGISProject('current')
m = p.listMaps()[0]
l = m.listLayers()[0]
if l.supports('DefinitionQuery'):
  #Get the list of definition queries
  dql = l.listDefinitionQueries()
  #Clear active definition queries otherwise the update will fail if there is already an active query
  for dq in dql:
    dq['isActive'] = False
  #Create a new definition query and append it to the list
  dql.append({'name': 'Appended Query', 'sql': "name = 'Lake Superior'", 'isActive': True})
  #Update the definition queries with the newly modified list
  l.updateDefinitionQueries(dql)