arcmap_python_LabelClass
目录
http://help.arcgis.com/zh-cn/arcgisdesktop/10.0/help/index.html#//00s30000002t000000
摘要
Provides access to a layer’s label class properties
讨论
The LabelClass object is essential for managing properties, such as label expressions or SQL queries, that are associated with a layer’s individual label classes.
Access to these properties is essential when, for example, a map document’s layers are redirected to a new workspace. The label classes’ SQL query may need to be updated with the appropriate syntax for the new database it is being executed against. For example,
field names in a personal geodatabase are surrounded by square brackets while field names in the file geodatabase are surrounded with double quotes. In addition to field names, other SQL properties (wildcard characters, other special characters, operators,
and so on) may need to be changed as well. If the SQL query is not updated, layers may fail to draw. For more information on these special cases, refer to theUpdating
and fixing data sources within arcpy.mapping topic.
The label expression is either using the VBScript or JScript parsers. The syntax and/or special characters for the parsers should not change (for example, VBScript always uses square brackets), but realize that the field names may change. Area and perimeter are
commonly used fields in an expression, and these do vary in name from data source to data source.
Not all layers support the labelClasses property, so it is useful to test this ahead of time using the
supports method—for example,layer.supports(“SHOWLABELS”) or layer.supports(“LABELCLASSES”).
If a layer supports labels, it also will support the labelClasses property, so you don’t need to test for both.
The labelClasses property will return a list of LabelClass objects. To reference a specific LabelClass object, it will be necessary to loop through each item
in the list or provide a specific index number.
属性
| 属性 | 说明 | 数据类型 |
|
className
（可读写）
|
Provides the ability to get or set a layer’s individual label class name. |
String |
|
expression
（可读写）
|
Provides the ability to get or set a layer’s individual label class expression. This can be as simple as a single field or more advanced using either a VBScript or JScript expression. |
String |
|
SQLQuery
（可读写）
|
Provides the ability to get or set a layer’s individual label class SQLQuery. This is useful for restricting labels to certain features. |
String |
|
showClassLabels
（可读写）
|
Provides the ability get or set the visibility of individual label classes. |
Boolean |
代码示例
The following script will print the label class properties for only those layers that have labels and individual label classes turned on. The script first confirms that the layer supports the labelClasses property.
import arcpy
mxd = arcpy.mapping.MapDocument(r"C:\Project\Project.mxd")
for lyr in arcpy.mapping.ListLayers(mxd):
if lyr.supports("LABELCLASSES"):
if lyr.showLabels:
print "Layer name: " + lyr.name
for lblClass in lyr.labelClasses:
if lblClass.showClassLabels:
print " Class Name: " + lblClass.className
print " Expression: " + lblClass.expression
print " SQL Query: " + lblClass.SQLQuery
del mxd
The following script will modify the SQL query that once pointed to a personal geodatabase, but now its layer references a file geodatabase. Square brackets will be changed to double quotes and the wildcard character will be modified from an asterisk (*) to
a percent symbol (%). A new output map document is saved, preserving the original map document.
import arcpy
mxd = arcpy.mapping.MapDocument(r"C:\Project\Project.mxd")
for lyr in arcpy.mapping.ListLayers(mxd):
if lyr.supports("LABELCLASSES"):
for lblClass in lyr.labelClasses:
lblClass.SQLQuery = lblClass.SQLQuery.replace("[", "\"")
lblClass.SQLQuery = lblClass.SQLQuery.replace("]", "\"")
lblClass.SQLQuery = lblClass.SQLQuery.replace("*", "%")
mxd.saveACopy("c:/project/project2.mxd")
del mxd
转载自：https://blog.csdn.net/zzh_my/article/details/8122182
