Module 6: Geoprocessing Scripts

Processing loops and decisions

AML (Arc Macro Language) VB script Jscript PERL Python (comes with ArcGIS) Most COM compliant scripting languages

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

Installing Python ArcGIS Desktop CD Explore rather than open to avoid autoinstallation of ArcGIS

In Python folder.. Run both exe files

GeoProcessor Object

Export Model to Script

# 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") # Set the ArcGIS product code (Arcview, ArcEditor, or ArcInfo) gp.SetProduct("ArcInfo") Python system String module Operating System COM Dispatch

# Load required toolboxes... gp.AddToolbox("C:/workshop_geoprocessing/ExampleToolbox.tbx") # 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)

# 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)

# use + to concatenate strings: # single or double-quotes enclose string chars name = ‘moose_locations’ type = “.shp” shapefile = name + type print shapefile moose_locations.shp

# decisions or branching: # indentation used to indicate structure if type == 'point' : print 'Theme is point type' print 'Must be polygon type to use erase tool' elif type == 'polyline' : print 'Theme is polyline type' print 'Convert to polygon type, then rerun script' elif type == 'polygon' : print 'Theme is polygon type' print 'Correct feature type for using erase tool' else : print "Theme type is not point, line, or polygon" print “End of Script” #out of if block

Listing Data

List first 2 pond polygon feature classes # 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("pond*","polygon") fcs.reset() #get first two objects in list and assign to variables theme1, theme2: theme1 = fcs.next() theme2 = fcs.next() print "First two polygon themes in workspace: ", str(theme1), str(theme2)

List all pond polygon feature classes # 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("pond*","polygon") fcs.reset() # Get the first theme and start the loop Current_Theme = fcs.next() while Current_Theme: # While the Current_Theme is not empty Print “Current theme in list is:”, str(Current_Theme) Current_Theme = fcs.next() Print “End of Script”

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("pond*","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"

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

Test Batch Process….

Scheduling Scripts

Sources of Confusion Python commands and variables are case sensitive ( print theme <> Print theme <> print Theme ) Geoprocessor properties not case sensitive ( gp.workspace = gp.WorkSpace ) \ is a reserved character meaning line continuation (use / or \\ for paths instead of \) Indentation is a source of loop structure

Sources of Confusion Model does not use UML like ArcObjects Arrows indicate instantiation Only non character properties are indicated in diagram