UpdateCursor

Resumen

UpdateCursor establishes read-write access to records returned from a feature class or table.

Returns an iterator of lists. The order of values in the list matches the order of fields specified by the field_names argument.

Learn more about data access using cursors

Debate

Update cursors can be iterated using a for loop. Update cursors also support with statements to reset iteration and aid in removal of locks. However, using a del statement to delete the object or wrapping the cursor in a function to have the cursor object go out of scope should be considered to guard against all locking cases.

La apertura de operaciones de inserción o actualización simultáneas en el mismo espacio de trabajo con distintos cursores requiere que se inice una sesión de edición.

A continuación, se incluyen algunos tipos de datasets que solo se pueden editar en una sesión de edición:

• Clases de entidad que forman parte de una topología
• Clases de entidad que forman parte de una red geométrica
• Clases de entidad que forman parte de un dataset de red
• Datasets versionados en geodatabases corporativas
• Algunas clases de entidad y objetos con extensiones de clase

In Python 2, UpdateCursor supports the iterator next method to retrieve the next row outside of a loop. In Python 3, the equivalent is performed by using the Python built-in next function.

Nota:

The Calculate Field and Calculate Fields tools can also be used to update field values.

Nota:

Using an UpdateCursor on a layer with a joined table is not supported.

Sintaxis

UpdateCursor (in_table, field_names, {where_clause}, {spatial_reference}, {explode_to_points}, {sql_clause}, {datum_transformation}, {explicit}, {spatial_filter}, {spatial_relationship}, {search_order})

Parámetro	Explicación	Tipo de datos
in_table	The feature class, layer, table, or table view.	String
field_names [field_names,...]	A list (or tuple) of field names. For a single field, you can use a string instead of a list of strings. Use an asterisk (*) instead of a list of fields to access all fields from the input table (BLOB fields are excluded). However, for faster performance and reliable field order, it is recommended that the list of fields be narrowed to only those that are actually needed. Raster fields are not supported. Additional information can be accessed using tokens (such as OID@) in place of field names: SHAPE@XY—Una tupla de las coordenadas x,y del centroide de la entidad. SHAPE@XYZ—Una tupla de las coordenadas x, y, z del centroide de la entidad. SHAPE@TRUECENTROID—Una tupla de las coordenadas x,y del centroide de la entidad. Devuelve el mismo valor que SHAPE@XY. SHAPE@X—Un doble de la coordenada x de la entidad. SHAPE@Y—Un doble de la coordenada y de la entidad. SHAPE@Z—Un doble de la coordenada z de la entidad. SHAPE@M—Un doble del valor m de la entidad. SHAPE@JSON—La cadena de caracteres JSON de Esri que representa la geometría. SHAPE@WKB—Representación binaria conocida (WKB) para geometría OGC. Ofrece una representación portátil de un valor de geometría como una transmisión contigua de bytes.Los valores se devuelven como un objeto bytearray, pero se pueden actualizar como un objeto bytearray o bytes. SHAPE@WKT—Representación en texto conocida (WKT) para geometría OGC. Ofrece una representación portátil de un valor de geometría como cadena de caracteres. SHAPE@—Objeto de geometría para la entidad. SHAPE@AREA—Un doble del área de la entidad. SHAPE@LENGTH—Un doble de la longitud de la entidad. CREATED@—Un objeto datetime de cuándo se creó la entidad. Este campo es de solo lectura. CREATOR@—Una cadena del nombre de usuario que creó la entidad. Este campo es de solo lectura. EDITED@—Un objeto datetime de cuándo se editó la entidad por última vez. Este campo es de solo lectura. EDITOR@—Una cadena del nombre de usuario que editó la entidad por última vez. Este campo es de solo lectura. GLOBALID@—Una cadena de caracteres del identificador único universal de la entidad. Este campo es de solo lectura. OID@—El valor del campo Id. de objeto. SUBTYPE@—Un entero del código de subtipo.	String
where_clause	An optional expression that limits the records returned. For more information on WHERE clauses and SQL statements, see SQL reference for query expressions used in ArcGIS. (El valor predeterminado es None)	String
spatial_reference	The spatial reference of the feature class. When this argument is specified, the feature will be projected (or transformed) from the input's spatial reference. If unspecified, the input feature classes' spatial reference will be used. Valid values for this argument are a SpatialReference object or string equivalent. (El valor predeterminado es None)	SpatialReference
explode_to_points	Deconstruct a feature into its individual points or vertices. If explode_to_points is set to True, a multipoint feature with five points, for example, is represented by five rows. (El valor predeterminado es False)	Boolean
sql_clause	A pair of SQL prefix and postfix clauses organized in a list or tuple. An SQL prefix clause supports None, DISTINCT, and TOP. An SQL postfix clause supports None, ORDER BY, and GROUP BY. Use DISTINCT in a prefix clause. with arcpy.da.UpdateCursor( in_features, ["OID@", "STREET_NAME"], sql_clause=("DISTINCT STREET_NAME", None) ) as cur: Use TOP in a prefix clause and ORDER BY in a postfix clause. with arcpy.da.UpdateCursor( in_features, ['OID@', "ELEVATION"], sql_clause=("TOP 5", "ORDER BY ELEVATION DESC") ) as cur: Use GROUP BY in a postfix clause. with arcpy.da.UpdateCursor( in_features, ['STREET_NAME'], sql_clause=(None, "GROUP BY STREET_NAME") ) as cur: An SQL prefix clause is positioned in the first position and will be inserted between the SELECT keyword and the SELECT COLUMN LIST. The SQL prefix clause is most commonly used for clauses such as DISTINCT or ALL. An SQL postfix clause is positioned in the second position and will be appended to the SELECT statement, following the where clause. The SQL postfix clause is most commonly used for clauses such as ORDER BY. Nota: DISTINCT, ORDER BY, and ALL are only supported when working with databases. They are not supported by other data sources (such as dBASE or INFO tables). TOP is only supported by SQL Server databases. (El valor predeterminado es (None, None))	tuple
datum_transformation	When the cursor projects the features from one spatial reference to another, if the spatial references do not share the same datum, an appropriate datum transformation should be specified. An update cursor can perform a projection or transformation at two stages: when reading the features from the feature class on disk and when writing the updated features into the feature class. The ListTransformations function can be used to provide a list of valid datum transformations between two spatial references. Learn more about datum transformations	String
explicit [explicit,...]	If a field has a default value and the field is nullable, using a value of True will explicitly override the default value and insert null values into the record. When using a value of False, the default value will be inserted instead of null. Apply the explicit rule to all fields: with arcpy.da.UpdateCursor(table, [field1, field2, field3], explicit=True) as cursor: ... The explicit rule can also be applied to individual fields using a list of Boolean values. The list of values must be the same length as the list of fields. Apply the explicit rule to only the first two fields: with arcpy.da.UpdateCursor(table, [field1, field2, field3], explicit=[True, True, False]) as cursor: ... (El valor predeterminado es False)	Boolean
spatial_filter	A geometry object used to spatially filter features. When this argument is specified, the cursor will limit the features returned, based on specified geometry and the spatial_relationship value. (El valor predeterminado es None)	Geometry
spatial_relationship	The spatial relationship between the input and the query geometry in the spatial_filter argument. This argument is only applicable when specifying the spatial_filter argument. INTERSECTS— Rows are only returned when the spatial_filter geometry intersects the input row's geometry. ENVELOPE_INTERSECTS— Rows are only returned when the spatial_filter geometry's envelope intersects the input row's geometry. INDEX_INTERSECTS— Rows are only returned when the spatial_filter geometry's envelope intersects the index entry for the input row's geometry. Because it uses the underlying index grid, rather than the envelope of the feature, it is faster and is commonly used for return features for display purposes. TOUCHES— Rows are only returned when the spatial_filter geometry touches the input row's geometry. OVERLAPS— Rows are only returned when the spatial_filter geometry overlaps the input row's geometry. CROSSES— Rows are only returned when the spatial_filter geometry crosses the input row's geometry. WITHIN— Rows are only returned when the spatial_filter geometry is within the input row's geometry. CONTAINS— Rows are only returned when the spatial_filter geometry contains the input row's geometry. (El valor predeterminado es INTERSECTS)	String
search_order	The order in which the spatial searches are applied by the RDBMS. This property only affects enterprise geodatabase data and is only applicable when specifying the spatial_filter argument. ATTRIBUTEFIRST—The attribute query will be applied first. SPATIALFIRST— The spatial query will be applied first. (El valor predeterminado es ATTRIBUTEFIRST)	String

Propiedades

Propiedad	Explicación	Tipo de datos
fields (Sólo lectura)	A tuple of field names used by the cursor. The tuple will include all fields and tokens specified by the field_names argument. The order of the field names on the fields property will be the same as passed in with the field_names argument. If the field_names argument is set to *, the fields property will include all fields used by the cursor. A value of * will return geometry in a tuple of x,y coordinates (equivalent to the SHAPE@XY token).	tuple

Descripción general del método

Método	Explicación
deleteRow ()	Deletes the current row.
reset ()	Resets the cursor back to the first row.
updateRow (row)	Updates the current row in the table.

Métodos

deleteRow ()

reset ()

updateRow (row)

Parámetro	Explicación	Tipo de datos
row	A list or tuple of values. The order of values should be in the same order as the fields. When updating fields, if the incoming values match the type of field, the values will be cast as necessary. For example, a value of 1.0 to a string field will be added as "1.0", and a value of "25" added to a float field will be added as 25.0.	tuple

Muestra de código

UpdateCursor example 1

Use UpdateCursor to update a field value by evaluating the values of other fields.

import arcpy

fc = 'c:/data/base.gdb/well'
fields = ['WELL_YIELD', 'WELL_CLASS']

# Create update cursor for feature class 
with arcpy.da.UpdateCursor(fc, fields) as cursor:
    # For each row, evaluate the WELL_YIELD value (index position 
    # of 0), and update WELL_CLASS (index position of 1)
    for row in cursor:
        if (row[0] >= 0 and row[0] <= 10):
            row[1] = 1
        elif (row[0] > 10 and row[0] <= 20):
            row[1] = 2
        elif (row[0] > 20 and row[0] <= 30):
            row[1] = 3
        elif (row[0] > 30):
            row[1] = 4

        # Update the cursor with the updated list
        cursor.updateRow(row)

UpdateCursor example 2

Use UpdateCursor to update a field of buffer distances for use with the Buffer function.

import arcpy

arcpy.env.workspace = 'c:/data/output.gdb'
fc = 'c:/data/base.gdb/roads'
fields = ['ROAD_TYPE', 'BUFFER_DISTANCE']

# Create update cursor for feature class 
with arcpy.da.UpdateCursor(fc, fields) as cursor:
    # Update the field used in Buffer so the distance is based on road 
    # type. Road type is either 1, 2, 3, or 4. Distance is in meters. 
    for row in cursor:
        # Update the BUFFER_DISTANCE field to be 100 times the 
        # ROAD_TYPE field.
        row[1] = row[0] * 100
        cursor.updateRow(row) 

# Buffer feature class using updated field values
arcpy.analysis.Buffer(fc, 'roads_buffer', 'BUFFER_DISTANCE')

UpdateCursor example 3

Use UpdateCursor with a spatial filer to update field values.

import arcpy

arr = arcpy.Array(
    [arcpy.Point(342917.4, 553980.8), arcpy.Point(366915.9, 594749.1)]
)
new_road = arcpy.Polyline(arr, spatial_reference=arcpy.SpatialReference(26971))

fc = r"C:\data\chicago.gdb\houses"
fields = ["OCCUPIED"]

with arcpy.da.UpdateCursor(
    fc, fields, where_clause="OCCUPIED != 'Vacant'", spatial_filter=new_road
) as cursor:
    for row in cursor:
        row[0] = 'Vacant'
        cursor.updateRow(row)