2006 GIS Jam: ArcGIS Python Scripting

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2006 GIS Jam ArcGIS Python Scripting
http//nrm.salrm.uaf.edu/dverbyla/arcgis_python
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Getting Started With Python Geoprocessing

• Why use scripting with ArcGIS?
• Python Basics
• ArcGIS Geoprocessor Basics
• Simple Applications
• Sources of confusion

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Why bother with scripting?
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When NOT to bother with scripting?
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Scripting Languages for Geoprocessing

• VB script
• Jscript
• PERL
• Python (comes with ArcGIS)

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Python

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

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GeoProcessor Model
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Export Model to Script
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ArcGIS Geoprocessor Basics

• Import modules
• Create geoprocessor object
• Use geoprocessor

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polygon_to_poly_line.py Created on Fri Dec
31 2004 123454 PM (generated by
ArcGIS/ModelBuilder) Import system
modulesimport sys, string, os,
win32com.client Create the Geoprocessor
objectgp win32com.client.Dispatch("esriGeoproces
sing.GpDispatch.1") Local variables...poly_lin
es_shp "C/temp/poly_lines.shp"selected_polygon
s_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

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OR
OR
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Script arguments or variables...Input_Features
sys.argv1Output_Feature_Class
sys.argv2 Process Polygon To
Line...gp.toolbox "C/temp/My
Toolbox.tbx"gp.PolygonToLine(Input_Features,
Output_Feature_Class)
Script Arguments---input from user
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Running python scripts

• Using PythonWin debugger
• Using Python command window
• As system process
• As scheduled process

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PythonWin
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1) Check for syntax errors
2) Step Through Script Using Debugger
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Thousands of Toolbars Bog Down System To A Crawl!
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Easy Fix comment out self.SaveBarState(ToolbarD
efault)
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Python command window
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Running script as system process
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Scheduling Scripts
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Messages From Executing Tools
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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

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Convert all pond polygon to line themes
Import system modules import sys, string, os,
win32com.client Create the Geoprocessor
object gp win32com.client.Dispatch("esriGeoproce
ssing.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"
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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

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Interpreted Line by Line SLOW
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Case Sensitive
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Indentation Source of Structure
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/ is a reserved character is a comment character
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Determine shape type of every theme listed in
text file..
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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/