2006 GIS Jam: ArcGIS Python Scripting

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

Why bother with scripting?

When NOT to bother with scripting?

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

Python Platform independent (linux, unix, windows) Object-oriented, developer language Good website ( Comes with ArcGIS, free from web

GeoProcessor Model

Export Model to Script

ArcGIS Geoprocessor Basics Import modules Create geoprocessor object Use geoprocessor

# polygon_to_poly_line.py # Created on: Fri Dec :34:54 PM # (generated by ArcGIS/ModelBuilder) # Import system modules import sys, string, os, win32com.client # Create the Geoprocessor object gp =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

OR

# 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) Script Arguments---input from user

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

PythonWin

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

Thousands of Toolbars Bog Down System To A Crawl!

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

Python command window

Running script as system process

Scheduling Scripts

Messages From Executing Tools

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

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"

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

Interpreted Line by Line = SLOW

Case Sensitive

Indentation Source of Structure

/ is a reserved character # is a comment character

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

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