摘要
UpdateCursor 函数创建一个用于更新或删除指定要素类、shapefile 和表中的行的游标。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
以迭代方式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,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, shapefile, or table containing the rows to be updated or deleted. | String |
where_clause | 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 [fields,...] | The fields to be included in the cursor. By default, all fields are included. | String |
sort_fields | Fields used to sort the rows in the cursor. Ascending and descending order for each field is denoted by A and D. | String |
返回值
数据类型 | 说明 |
Cursor | 游标对象可分发行对象。 |
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