1. 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

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

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

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

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

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

7. Demo
Data structures
Python – Beyond the Basics

8. Script tools
Python – Beyond the Basics

9. Demo
Quadrat Analysis tool
Python – Beyond the Basics

10. 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

11. 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

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

13. 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

14. arcpy classes
Python – Beyond the Basics

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

16. 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

17. Using classes for parameters
Extent
SpatialReference
Python – Beyond the Basics

18. 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

19. 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

20. 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

21. Cursors
Python – Beyond the Basics

22. 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

23. 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

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

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

26. Demo
arcpy.da cursors
Python – Beyond the Basics

27. Geometry
Python – Beyond the Basics

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

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

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

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

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

33. 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

34. 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 –
Paper – pick up and put in drop box
Python – Beyond the Basics

35. Python – Beyond the Basics