Python – Beyond the Basics 2013 Esri International User Conference July 8–12, 2013 | San Diego, California Technical Workshop Python – Beyond the Basics David Wynne, Ken Smith

Data structures & functions Agenda Data structures & functions Classes Geometry 1 2 3 4 5 Script tools Cursors Python – Beyond the Basics

Python 201: Data structures & functions Python – Beyond the Basics

Key Python data structures Lists Tuples Flexible Immutable Ordered Dictionary Key/value pairs Python – Beyond the Basics

List comprehension Compact way of mapping a list into another Python – Beyond the Basics

Defining Functions Organize and re-use functionality Define your function Return a result Call the function Python – Beyond the Basics

Demo Data structures Python – Beyond the Basics

Script tools Python – Beyond the Basics

Demo Quadrat Analysis tool Python – Beyond the Basics

Geoprocessing Framework and Python Tools can be called from Python Python code can be turned into a tool A script tool… Looks and behaves like any system tool Provides default validation Has no UI programming Python – Beyond the Basics

Script tools Tools have parameters Script tools support messages Use GetParameterAsText (or GetParameter) to get inputs Script tools support messages arcpy.AddMessage arcpy.AddWarning arcpy.AddError Python – Beyond the Basics

Tip: Script Template http://esriurl.com/4558 Python – Beyond the Basics

Quadrat Analysis tool Part B: Jump start your analysis with a template Demo Quadrat Analysis tool Part B: Jump start your analysis with a template Python – Beyond the Basics

arcpy classes Python – Beyond the Basics

arcpy classes Classes are used to create objects Frequently used for… Tool parameters Working with geometry Python – Beyond the Basics

arcpy Classes Most tool parameters are easily defined with a string or number Some are not: Spatial reference Field map Classes can be used to define these parameters Python – Beyond the Basics

Using classes for parameters Extent SpatialReference Python – Beyond the Basics

Quadrat Analysis tool Part C: Extent class Cursors Chi-square function Demo Quadrat Analysis tool Part C: Extent class Cursors Chi-square function Python – Beyond the Basics

Recap Fast development A script template gets you started Easy access to tools and functions through arcpy No UI development required Script tools provide default validation Python – Beyond the Basics

Recap… Used a function to define / group useful functionality Used open source libraries (numpy) Easy to share and deploy No ArcObjects or dlls to register Python – Beyond the Basics

Cursors Python – Beyond the Basics

Cursors Use cursors to access records and features Two varieties ‘Classic’ cursors ‘Data access’ cursors (new at 10.1) SearchCursor Read-only UpdateCursor Update or delete rows InsertCursor Insert rows Python – Beyond the Basics

Cursor mechanics Data access cursors use lists and tuples Values are accessed by index Classic cursors use row objects Values are accessed by setValue/getValue Python – Beyond the Basics

With statements arcpy.da Cursors support with statements Python – Beyond the Basics

Cursor performance Use only those fields you need Use tokens Get only what you need Full geometry is expensive Python – Beyond the Basics

Demo arcpy.da cursors Python – Beyond the Basics

Geometry Python – Beyond the Basics

Geometry and cursors Can create geometry in different ways Geometry objects List of coordinates Using other formats JSON, WKT, WKB Python – Beyond the Basics

Geometry and cursors Can create geometry in different ways Geometry objects List of coordinates Using other formats JSON, WKT, WKB Python – Beyond the Basics

Working with geometry Relational: Is a point within a polygon? Python – Beyond the Basics

Working with geometry Topological What is the intersection of two geometries? Python – Beyond the Basics

Working with geometry Others What is the halfway point of a line? What is the geodesic area of a polygon? Python – Beyond the Basics

Resources Python resource center ArcPy Café Python at UC 2013 pro.arcgis.com/analysis/python/ ArcPy Café arcpy.wordpress.com Python at UC 2013 esriurl.com/uc13python Python – Beyond the Basics

First Offering ID (Tues.): 1210 Second Offering ID (Wed.): 1311 Thank you… Please fill out the session evaluation First Offering ID (Tues.): 1210 Second Offering ID (Wed.): 1311 Online – www.esri.com/ucsessionsurveys Paper – pick up and put in drop box Python – Beyond the Basics

Python – Beyond the Basics