nrm.salrm.uaf/~dverbyla/arcgis_python

1. ArcGIS Python Scripting WorkshopDave VerbylaDepartment of Forest SciencesSchool of Natural Resources and Agricultural SciencesUniversity of Alaska Fairbanks http://nrm.salrm.uaf.edu/~dverbyla/arcgis_python

2. Getting Started With Python Geoprocessing • Why use scripting with ArcGIS? • Python Basics • ArcGIS Geoprocessor Basics • Simple Applications • Sources of confusion

3. Why bother with scripting?

4. When NOT to bother with scripting?

8. Scripting Languages for Geoprocessing • VB script • Jscript • PERL • Python (comes with ArcGIS)

9. Python • Platform independent (linux, unix, windows) • Object-oriented, developer language • Good website (www.python.org) • Comes with ArcGIS, free from web

10. GeoProcessor Model

13. Export Model to Script

14. ArcGIS Geoprocessor Basics • Import modules • Create geoprocessor object • Use geoprocessor

15. # polygon_to_poly_line.py# Created on: Fri Dec 31 2004 12:34:54 PM# (generated by ArcGIS/ModelBuilder)# Import system modulesimport sys, string, os, win32com.client# Create the Geoprocessor objectgp =win32com.client.Dispatch("esriGeoprocessing.GpDispatch.1")# Local variables...poly_lines_shp = "C:/temp/poly_lines.shp"selected_polygons_shp = "C:/temp/selected_polygons.shp"# Process: Polygon To Line...gp.toolbox = "C:/workshop_geoprocessing/ExampleToolbox.tbx"gp.PolygonToLine(selected_polygons_shp, poly_lines_shp) • Python system • String module • Operating System • COM Dispatch

16. OR OR

17. Script Arguments---input from user # Script arguments or variables...Input_Features = sys.argv[1]Output_Feature_Class = sys.argv[2]# Process: Polygon To Line...gp.toolbox = "C:/temp/My Toolbox.tbx"gp.PolygonToLine(Input_Features, Output_Feature_Class)

18. Running python scripts • Using PythonWin debugger • Using Python command window • As system process • As scheduled process

19. PythonWin

20. 1) Check for syntax errors 2) Step Through Script Using Debugger

22. Thousands of Toolbars Bog Down System To A Crawl!

23. “Easy Fix”— comment out self.SaveBarState(ToolbarDefault)

24. Python command window

25. Running script as system process

26. Scheduling Scripts

29. Messages From Executing Tools

30. Example Applications For every polygon theme in workspace • Convert polygon theme to polyline theme • Compute area and perimeter in all themes For every workspace in text file: • Build raster pyramids for every raster in each workspace

31. Convert all pond polygon to line themes # Import system modules import sys, string, os, win32com.client # Create the Geoprocessor object gp = win32com.client.Dispatch("esriGeoprocessing.GpDispatch.1") #set workspace gp.workspace = "C:/ponds"; print "workspace set to: ", str(gp.workspace) #get list of feature classes fcs = gp.ListFeatureClasses("*","polygon") fcs.reset() print "All pond polygon themes will be converted to pond shoreline themes..." # Get the first theme and start the loop Current_Theme = fcs.next() while Current_Theme: # While the Current_Theme is not empty print "Converting Theme:", str(Current_Theme) gp.PolygonToLine(Current_Theme, "c:/shorelines/" + Current_Theme) Current_Theme = fcs.next() print "End of Script"

38. Problems With Python Scripting • Interpreted language • Case sensitive • Indentation source of structure • \ is a reserved character • # is a commenting character • Newline character at end of lines

39. Interpreted Line by Line = SLOW

40. Case Sensitive

41. Indentation Source of Structure

42. / is a reserved character# is a comment character

43. Determine shape type of every theme listed in text file…..

46. More information Python • http://wiki.python.org/moin/BeginnersGuide • http://www.python.org/ • http://diveintopython.org/ ArcGIS Python Scripting • http://hobu.biz/software/python_guide_esri/ • http://arcscripts.esri.com/