arcpy.Describe and arcpy.List*

Describing objects

ArcGIS interacts with a number of types of objects

arcpy.Describe(object) exposes object properties that can be used in Python to control program flow, tool parameter values, etc. of geoprocessing scripts

e.g. Clip all polyline feature classes in a workspace.

Overview

gp.Describe(object) Describe object

gp.List* Python list of objects

ArcGIS 9.3

ArcGIS 10arcpy.Describe(object)arcpy.List*

9.2 9.3

Evolution Describe Object Properties

An example of how Python is evolvingwith ArcGIS

Describing data in 10.x

Describe Example (feature class)

… if you plan to do multiples in same workspace

Describe a Feature Class

Describe a Geodatabase

some are case sensitive, others notarcpy.env.workspace is

Fields in a Feature Class via Describe

ArcGIS 8.x, 9.x

ArcGIS 10

Describe a Raster

List functions

Scripts allow you to iterate through lists

arcpy provides many list functions that create lists of objects

e.g. For each feature class in a given workspace, create a report that shows how many are point, line, and polygon (uses ListFeatureClasses and Describe)

Lists of Objects in Geoprocessing OMD

Listing Data

List*: Python List (i.e. returns a Python List)

Know number of * in a Python list

Use a for loop

ListFeatureClasses([wildCard], [FeatureType])

ListFeatureClasses examples

ListFields(pInputValue, [wild card], [FieldType])

Same Field object as each Field object in list thatis returned by Fields propertyof the Describe Object

ListFields examples

os.walk(top, topdown=True, onerror=None,

followlinks=False)

os.walk() simple example

os.walk() not-so-simple example

Find all Flash videos (SWF) in the entire tree under a given root folderIf the SWF file has the “slide”, and not “group”, as part of its name convert the first frame of the video to a JPG with the name of the SWF

Dependencies

Python for Windows ExtensionsInterfacing with Windows, Windows applications & librariesExamples @ http://win32com.goermezer.de/content/category/7/87/189/

SWF To Image ActiveX libraryhttps://bytescout.com/download/download_freeware.html

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os.walk() not-so-simple example