Cursor

Zusammenfassung

A cursor is a data access object that can be used 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.

Vorversion:

The cursor functions and Cursor object only remain for use in legacy scripts. When authoring or updating scripts, it is recommended that you use the cursors in the arcpy.da module. The arcpy.da cursors provide improved performance and functionality, and support for newer field types and tokens.

Methodenübersicht

Methode	Erläuterung
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.

Methoden

deleteRow (row)

Parameter	Erläuterung	Datentyp
row	The row to be deleted.	Row

insertRow (row)

Parameter	Erläuterung	Datentyp
row	The row to be inserted.	Row

newRow ()

Rückgabewert

Datentyp	Erläuterung
Row	A new empty Row object.

next ()

Rückgabewert

Datentyp	Erläuterung
Object	The next object at the current index.

reset ()

updateRow (row)

Parameter	Erläuterung	Datentyp
row	The row used to update the current position of the cursor.	Row

Codebeispiel

Cursor example 1

Use a search cursor to view field values in rows.

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 rows in a 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