UpdateCursor

摘要

更新或删除指定要素类或表上的属性值行。

该游标将数据锁定保留至脚本完成或更新游标对象被删除时。

说明

旧版本：

自 ArcGIS 10.1 起，此功能已由 arcpy.da.UpdateCursor 取代。 为了获得更快性能，请使用 arcpy.da.UpdateCursor。

可用于迭代更新游标的方式有两种：for 循环或者 while 循环（通过游标的 next 方法返回下一行）。 如果要使用游标的 next 方法来检索行数为 N 的表中的所有行，则脚本必须调用 next N 次。 在检索完结果集的最后一行后调用 next 将返回 None，它是一种 Python 数据类型，此处用作占位符。

通过 for 循环使用 UpdateCursor。

import arcpy

fc = "c:/data/base.gdb/roads"
field1 = "field1"
field2 = "field2"

cursor = arcpy.UpdateCursor(fc)
for row in cursor:
    # field2 will be equal to field1 multiplied by 3.0
    row.setValue(field2, row.getValue(field1) * 3.0)
    cursor.updateRow(row)

通过 while 循环使用 UpdateCursor。

import arcpy

fc = "c:/data/base.gdb/roads"
field1 = "field1"
field2 = "field2"

cursor = arcpy.UpdateCursor(fc)
row = cursor.next()
while row:
    # field2 will be equal to field1 multiplied by 3.0
    row.setValue(field2, row.getValue(field1) * 3.0)
    cursor.updateRow(row)
    row = cursor.next()

语法

UpdateCursor (dataset, {where_clause}, {spatial_reference}, {fields}, {sort_fields})

参数	说明	数据类型
dataset	The feature class or table containing the rows to be updated or deleted.	String
where_clause	An expression that limits the rows returned in the cursor. For more information on where clauses and SQL statements, see SQL reference for query expressions used in ArcGIS.	String
spatial_reference	Coordinates are specified in the spatial_reference provided and converted on the fly to the coordinate system of the dataset.	SpatialReference
fields	A semicolon-delimited string of fields to be included in the cursor. By default, all fields are included.	String
sort_fields	The fields used to sort the rows in the cursor. Ascending and descending order for each field is denoted by A for ascending and D descending, using the form "field1 A;field2 B".	String

返回值

数据类型	说明
Cursor	可分布 Row 对象的 Cursor 对象。

代码示例

UpdateCursor 示例

根据另一个字段值更新要素类中的字段值。

import arcpy

# Create update cursor for feature class
rows = arcpy.UpdateCursor("c:/data/base.gdb/roads")

# Update the field used in buffer so the distance is based on the
# road type. Road type is either 1, 2, 3, or 4. Distance is in meters.
for row in rows:
    # Fields from the table can be dynamically accessed from the
    # row object. Here fields named BUFFER_DISTANCE and ROAD_TYPE
    # are used
    row.setValue("BUFFER_DISTANCE", row.getValue("ROAD_TYPE") * 100)
    rows.updateRow(row)

# Delete cursor and row objects to remove locks on the data.
del row
del rows