SearchCursor (arcpy.da)

Zusammenfassung

SearchCursor establishes read-only access to the records returned from a feature class or table.

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

Diskussion

Geometry properties can be accessed by specifying the token SHAPE@ in the list of fields.

Search cursors can be iterated using a For loop. Search cursors also support With statements; using a With statement will guarantee close and release of database locks and reset iteration.

The records returned by SearchCursor can be constrained to match attribute criteria and/or spatial criteria.

Accessing full geometry with SHAPE@ is an expensive operation. If only simple geometry information is required, such as the x,y coordinate of a point, use tokens such as SHAPE@XY, SHAPE@Z and SHAPE@M for faster, more efficient access.

Hinweis:

arcpy.da.SearchCursor should not to be confused with the arcpy.SearchCursor.

Syntax

SearchCursor (in_table, field_names, {where_clause}, {spatial_reference}, {explode_to_points}, {sql_clause})

Parameter	Erläuterung	Datentyp
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 if you want to access all fields from the input table (raster and 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 —A tuple of the feature's centroid x,y coordinates. SHAPE@TRUECENTROID —A tuple of the feature's true centroid x,y coordinates. SHAPE@X —A double of the feature's x-coordinate. SHAPE@Y —A double of the feature's y-coordinate. SHAPE@Z —A double of the feature's z-coordinate. SHAPE@M —A double of the feature's m-value. SHAPE@JSON — The esri JSON string representing the geometry. SHAPE@WKB —The well-known binary (WKB) representation for OGC geometry. It provides a portable representation of a geometry value as a contiguous stream of bytes. SHAPE@WKT —The well-known text (WKT) representation for OGC geometry. It provides a portable representation of a geometry value as a text string. SHAPE@ —A geometry object for the feature. SHAPE@AREA —A double of the feature's area. SHAPE@LENGTH —A double of the feature's length. OID@ —The value of the ObjectID field. Hinweis: SHAPE@JSON, SHAPE@WKB, and SHAPE@WKT tokens were made available at ArcGIS 10.1 Service Pack 1.	String
where_clause	An optional expression that limits the records returned. For more information on WHERE clauses and SQL statements, see Building a query expression and Specifying a query in Python. (Der Standardwert ist None)	String
spatial_reference	The spatial reference of the feature class. It can be specified with either a SpatialReference object or string equivalent. (Der Standardwert ist 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. (Der Standardwert ist False)	Boolean
sql_clause	An optional pair of SQL prefix and postfix clauses organized in a list or tuple. SQL prefix supports None, DISTINCT, and TOP. SQL postfix supports None, ORDER_BY, and GROUP_BY. An SQL prefix clause is positioned in the first position and will be inserted between the SELECT keyword and the SELECT COLUMN LIST. Most commonly used for clauses like 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. Most commonly used for clauses like ORDER BY. Hinweis: This functionality is only available when working with geodatabases. Other data sources do not support it. (Der Standardwert ist (None, None))	tuple

Eigenschaften

Eigenschaft	Erläuterung	Datentyp
fields (Schreibgeschützt)	A tuple of field names used by the cursor. The tuple will include all fields (and tokens) specified by the field_names argument. If the field_names argument is set to "*", the fields property will include all fields used by the cursor. When using "*", geometry values will be returned in a tuple of the x,y-coordinates (equivalent to the SHAPE@XY token).	tuple

Methodenübersicht

Methode	Erläuterung
next ()	Returns the next row as a tuple. The order of fields will be returned in the order they were specified when creating the cursor.
reset ()	Resets the cursor back to the first row.

Methoden

next ()

Rückgabewert

Datentyp	Erläuterung
tuple

reset ()

Codebeispiel

SearchCursor example 1

Use SearchCursor to step through a feature class, printing specific field values and the x,y coordinates of the point.

import arcpy

fc = "c:/data/base.gdb/well"
fields = ["WELL_ID", "WELL_TYPE", "SHAPE@XY"]

# For each row print the WELL_ID and WELL_TYPE fields, and the
#  the feature's x,y coordinates
#
with arcpy.da.SearchCursor(fc, fields) as cursor:
    for row in cursor:
        print("{0}, {1}, {2}".format(row[0], row[1], row[2]))

SearchCursor example 2

Use SearchCursor to return a set of unique field values.

import arcpy

fc = "c:/data/base.gdb/well"
field = "Diameter"

# Use SearchCursor with list comprehension to return a
#  unique set of values in the specified field
#
values = [row[0] for row in arcpy.da.SearchCursor(fc, (field))]
uniqueValues = set(values)
print(uniqueValues)

SearchCursor example 3

Use SearchCursor to return attributes using tokens.

import arcpy

fc = "c:/data/base.gdb/well"

# For each row print the Object ID field, and use the SHAPE@AREA
#  token to access geometry properties
#
with arcpy.da.SearchCursor(fc, ("OID@", "SHAPE@AREA")) as cursor:
    for row in cursor:
        print("Feature {0} has an area of {1}".format(row[0], row[1]))

SearchCursor example 4

Use SearchCursor with a where clause to identify features that meet specific criteria.

import arcpy

fc = "c:/base/data.gdb/roads"
class_field = "Road Class"
name_field = "Name"

# Create an expression with proper delimiters
#
expression = arcpy.AddFieldDelimiters(fc, name_field) + " = 2"

# Create a search cursor using an SQL expression
#
with arcpy.da.SearchCursor(fc, (class_field, name_field),
                           where_clause=expression) as cursor:
    for row in cursor:
        # Print the name of the residential road
        print(row[1])

SearchCursor example 5

Use SearchCursor and Python's sorted method to sort rows.

For additional sorting options see Python's Sorting Mini-HOW TO.

import arcpy

fc = "c:/data/base.gdb/well"
f1, f2 = "WELL_ID", "WELL_TYPE"

# Use Python's sorted method to sort rows
#
for row in sorted(arcpy.da.SearchCursor(fc, [f1, f2])):
    print("{0}, {1}".format(row[0], row[1]))