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Walk

Summary

Generate data names in a directory/database structure by walking the tree top-down or bottom-up. Each directory/workspace yields a tuple of three: directory path, directory names, and file names.

Discussion

Note:

The Walk function was made available at ArcGIS 10.1 Service Pack 1.

The Python os module includes an os.walk function that can be used to walk through a directory tree and find data. os.walk is file based and does not recognize database contents such as geodatabase feature classes, tables, or rasters. arcpy.da.Walk can be used to catalog data.

Syntax

Walk (top, {topdown}, {onerror}, {followlinks}, {datatype}, {type})
ParameterExplanationData Type
top

The top-level workspace that will be used.

String
topdown

If topdown is True or not specified, the tuple for a directory is generated before the tuple for any of its workspaces (workspaces are generated top-down). If topdown is False, the tuple for a workspace is generated after the tuple for all of its subworkspaces (workspaces are generated bottom-up).

When topdown is True, the dirnames list can be modified in-place, and Walk() will only recurse into the subworkspaces whose names remain in dirnames. This can be used to limit the search, impose a specific order of visiting, or even to inform Walk() about directories the caller creates or renames before it resumes Walk() again. Modifying dirnames when topdown is Falseis ineffective, because in bottom-up mode the workspaces in dirnames are generated before dirpath itself is generated.

(The default value is True)

Boolean
onerror

Errors are ignored by default. The onerror function will be called with an OSError instance.

The function can be used to report the error and continue with the walk or raise an exception to abort.

Note:

The file name is available as the filename attribute of the exception object.

(The default value is None)

Function
followlinks

By default, Walk() does not walk into connection files. Set followlinks to True to visit connection files.

(The default value is False)

Boolean
datatype

The data type to limit the results returned. Valid data types are the following:

  • AnyAll data types are returned. Equivalent to using None or skipping the argument.
  • CadDrawing
  • CadastralFabric
  • Container
  • FeatureClass
  • FeatureDataset
  • GeometricNetwork
  • LasDataset
  • Layer
  • Locator
  • Map
  • MosaicDataset
  • NetworkDataset
  • PlanarGraph
  • RasterCatalog
  • RasterDataset
  • RelationshipClass
  • RepresentationClass
  • Style
  • Table
  • Terrain
  • Text
  • Tin
  • Tool
  • Toolbox
  • Topology

Multiple data types are supported if entered as a list or tuple.

for dirpath, dirnames, filenames in arcpy.da.Walk(workspace,
    datatype=['MosaicDataset', 'RasterDataset']):

(The default value is None)

String
type

Feature and raster data types can be further limited by type.

  • AllAll types are returned. Equivalent to using None or skipping the argument.
  • AnyAll types are returned. Equivalent to using None or skipping the argument.

Valid feature types are the following:

  • Multipatch Only multipatch feature classes are returned.
  • MultipointOnly multipoint feature classes are returned.
  • PointOnly point feature classes are returned.
  • PolygonOnly polygon feature classes are returned.
  • PolylineOnly polyline feature classes are returned.

Valid raster types are:

  • BIL Esri Band Interleaved by Line file
  • BIP Esri Band Interleaved by Pixel file
  • BMP Bitmap graphic raster dataset format
  • BSQ Esri Band Sequential file
  • DAT ENVI DAT file
  • GIF Graphic Interchange Format for raster datasets
  • GRID Esri Grid raster dataset format
  • IMG ERDAS IMAGINE raster data format
  • JP2 JPEG 2000 raster dataset format
  • JPG Joint Photographic Experts Group raster dataset format
  • PNG Portable Network Graphic raster dataset format
  • TIF Tag Image File Format for raster datasets

Multiple data types are supported if entered as a list or tuple.

for dirpath, dirnames, filenames in arcpy.da.Walk(workspace,
    datatype='FeatureClass', type=['Polygon', 'Polyline']):

(The default value is None)

String
Return Value
Data TypeExplanation
Generator

Yields a tuple of three that includes the workspace, directory names, and file names.

  • dirpath is the path to the workspace as a string.
  • dirnames is a list of names of subdirectories and other workspaces in dirpath.
  • filenames is a list of names of nonworkspace contents in dirpath.
Note:

Names in the lists include only the base name; no path components are included. To get a full path (which begins with top) to a file or directory in dirpath, do os.path.join(dirpath, name).

Code sample

Walk example 1

Use the Walk function to catalog polygon feature classes.

import arcpy
import os

workspace = "c:/data"
feature_classes = []

walk = arcpy.da.Walk(workspace, datatype="FeatureClass", type="Polygon")

for dirpath, dirnames, filenames in walk:
    for filename in filenames:
        feature_classes.append(os.path.join(dirpath, filename))
Walk example 2

Use the Walk function to catalog raster data. Any rasters in a folder named back_up will be ignored.

import arcpy
import os

workspace = "c:/data"
rasters = []

walk = arcpy.da.Walk(workspace, topdown=True, datatype="RasterDataset")

for dirpath, dirnames, filenames in walk:
    # Disregard any folder named 'back_up' in creating list of rasters
    if "back_up" in dirnames:
        dirnames.remove('back_up')
    for filename in filenames:
        rasters.append(os.path.join(dirpath, filename))

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