Cursor

概要

A cursor is a data access object that can be used either to iterate through the set of rows in a table or to insert new rows into a table. Cursors have three forms: search, insert, or update. Cursors are commonly used to read and update attributes.

手法の概要

手法	説明
deleteRow (row)	Deletes a row in the database. The row corresponding to the current position of the cursor will be deleted.
insertRow (row)	Inserts a new row into the database.
newRow ()	Creates an empty Row object.
next ()	Returns the next object at the current index.
reset ()	Sets the current enumeration index (used by the next method) back to the first element.
updateRow (row)	The updateRow method can be used to update the row at the current position of an update cursor.

手法

deleteRow (row)

パラメーター	説明	データ タイプ
row	The row to be deleted.	Row

insertRow (row)

パラメーター	説明	データ タイプ
row	The row to be inserted.	Row

newRow ()

戻り値

データ タイプ	説明
Row	A new empty Row object.

next ()

戻り値

データ タイプ	説明
Object	The next object at the current index.

reset ()

updateRow (row)

パラメーター	説明	データ タイプ
row	The row used to update the current position of the cursor.	Row

コードのサンプル

Cursor example 1

Use search cursor to view field values in row.

import arcpy

# Set the workspace
arcpy.env.workspace = "c:/base/data.gdb"

# Create the search cursor
cursor = arcpy.SearchCursor("roads", '"TYPE" <> 4')

# Iterate through the rows in the cursor
for row in cursor:
    print("Name: {0},  CFCC code: {1}".format(row.NAME, row.CFCC))

del cursor, row

Cursor example 2

Use an update cursor to change field values in rows.

import arcpy

# Set the workspace
arcpy.env.workspace = "c:/base/data.gdb"

# Create the update cursor
cursor = arcpy.UpdateCursor("roads")

# Update the road buffer distance field based on road type.
#   Road type is either 1,2,3,4  Distance is in meters.
for row in cursor:
    row.setValue("BUFFER_DIST", row.getValue("TYPE") * 100)
    cursor.updateRow(row)

# Delete cursor and row objects
del cursor, row

Cursor example 3

Use an insert cursor to create new rows in table.

import datetime
import arcpy

# Create insert cursor for table
cursor = arcpy.InsertCursor("c:/base/data.gdb/roads_maint")

# Create 25 new rows. Set default values on distance and CFCC code
for i in range(1000, 1025):
    row = cursor.newRow()
    row.setValue('rowid', i)
    row.setValue('distance', 100)
    row.setValue('CFCC', 'A10')
    row.setValue('LastInsp', datetime.datetime.now())
    cursor.insertRow(row)

# Delete cursor and row objects
del cursor, row