UpdateCursor (arcpy)
サマリ
The UpdateCursor function creates a cursor that lets you update or delete rows on the specified feature class, shapefile, or table. The cursor places a lock on the data that will remain until either the script completes or the update cursor object is deleted.
説明
Update cursors are able to be iterated with a for loop or in a while loop using the cursor's next method to return the next row. When using the next method on a cursor to retrieve all rows in a table containing N rows, the script must make N calls to next. A call to next after the last row in the result set has been retrieved returns None, which is a Python data type that acts here as a placeholder.
Using UpdateCursor with a for loop.
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)
Using UpdateCursor with a while loop.
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()
構文
パラメータ | 説明 | データ タイプ |
dataset |
The feature class, shapefile, or table containing the rows to be updated or deleted. | String |
where_clause |
An optional expression that limits the rows returned in the cursor. For more information on WHERE clauses and SQL statements, see About_building_an_SQL_expression. | String |
spatial_reference |
Coordinates are specified in the spatial_reference provided and converted on the fly to the coordinate system of the dataset. | Object |
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 |
データ タイプ | 説明 |
Cursor |
A Cursor object that can hand out row objects. |
コードのサンプル
Update field values in feature class, based on another field's value.
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.BUFFER_DISTANCE = row.ROAD_TYPE * 100
rows.updateRow(row)
# Delete cursor and row objects to remove locks on the data
#
del row
del rows