Using Python in ArcGIS Steven Beothy May 28, 2013

Transcription

1 Using Python in ArcGIS 10.1 Steven Beothy May 28, 2013

2 Today s Agenda This seminar is designed to help you understand: 1) Python and how it can be used 2) What s new in Python in ArcGIS ) How to develop Add-ins for ArcGIS Desktop with Python

3 Python (The Essentials)

4 Why Python Fulfills the needs of our user community Simple and easy to learn Scalable Modular Object Oriented Easy to maintain Cross platform Established and active user community

5 What is ArcPy? ArcPy is a native Python site-package Includes code completion and intellisense Provides direct access to many ArcGIS modules Data access (new) Mapping (updated) Extensions - Spatial Analyst (updated) Network Analyst (new) Time (new)

6 Functions The ArcPy module contains functions that are necessary for performing scripting tasks Listing data Describing data Geodatabase management Validating table and field names Analyzing & Updating data Map production These functions allow users to automate manual tasks

7 Basics of Scripting Where do I write Python code? Python Window (ArcGIS), PyScripter & PyWin, text editors etc. Simple python excerpt: # The import statement imports the arcpy site package import arcpy # Variables are assigned using an = featureclass = r d:\data\roads.gdb\highways # Geoprocessing tools can be run using two methods arcpy.management.getcount(featureclass) # Using the management toolbox arcpy.getcount_management(featureclass) # Using the arcpy toolbox

8 Basics of Scripting (2) Proper Syntax Colons should be placed at the end of statements and conditions Indentations determine what is executed Operators (==, >, <,!=) Loops (for, while, list) # A simple if, else statement var = a if var == a : # Execute the indented lines print ( variable is a ) else: print ( variable is not a ) # while loop x = 1 while x <5: print (x) x = x+1 # for loop x =[1,2,3,4] for num in x: print (num)

9 Basics of Scripting (3) Case sensitivity Variables and functions etc. are all case sensitive Common error: name x is not defined Specifying file paths Using forward-slashes: d:/data/roads.gdb/highways Using back-slashes: r d:\data\roads.gdb\highways Functions & modules A module is where the function is located A function is used to perform a specific task arcpy.mapping.pdfdocumentcreate(r d:\maps\canada.pdf )

10 Demonstration I Python window Importing ArcPy Running a geoprocessing task using Python

11 What s new in Python in ArcGIS 10.1

12 Python Toolboxes Have a number of advantages over custom toolboxes Tools that work just like core geoprocessing tools Messages can be written to the results window A single place to edit parameter definitions, validation code, and source code) Implement licensing checks Create Value Table parameters Create composite data type i.e. A parameter than can accept a feature layer or a raster layer

13 Data Access Module Data Access Cursors (e.g. arcpy.da.searchcursor) Much faster than traditional cursors (e.g. arcpy.searchcursor) Support with statements No need to access the full geometry # Import arcpy reference library import arcpy # Print the tower id, type, and the feature s locations (lat, long) fields = [ TOWER_ID, TOWER_TYPE, SHAPE@XY ] with arcpy.da.searchcursor (r c:\data\utilities.gdb\towers, fields) as cursor: for row in cursor: print ( {0},{1},{2}.format(row[0], row[1], row[2]))

14 Accessing Geometry The geometry of features can be accessed using a new shape@ token Traditionally geometries slowed down the cursor since they could not be individually returned shape@area, shape@length, shape@xy, shape@m, shape@z, shape@truecentroid # Import arcpy reference library import arcpy # Calculate the sum (length) of all the ferry lines in Canada with arcpy.da.searchcursor(r c:\data\transportation.gdb\ferry","shape@length") as rows: print sum([row[0]for row in rows])

15 Writing Feature Geometry Insert cursors must be used to create new features Point and Array objects are used to create the feature parts Update cursors can be used to replace a row s existing geometry # Add a new ferry line to the ferry feature class using an InsertCursor with arcpy.da.insertcursor(r c:\data\transportation.gdb\ferry","shape@") as ferrycursor: # Create an array using a series of point objects ptlist = [arcpy.point( , ), arcpy.point( , )] linearray = arcpy.array(ptlist) # Create a stream polyline from the array polyline = arcpy.polyline (linearray) # Insert stream polyline into the dataset ferrycursor.insertrow([polyline])

16 Editor Class Allows use of edit sessions and operations to manage database transactions Similar to editing with the GUI (Editor Toolbar) Edits are temporary until saved and applied to the session fc = r Database Connections\Brampton.sde\brampton.jgp.schools workspace = os.path.dirname(fc) #Start an edit session since editing is usually tied to a specific database this variable must be provided. edit = arcpy.da.editor(workspace) #Edit session is started without undo/redo stack for versioned data. The second arg. states whether the data is versioned. edit.startediting(false, False) #Insert a row into the school table with arcpy.da.insertcursor(fc, ( NAME, SHAPE@ )) as schoolcursor: schoolcursor.insertrow([ School of Hard Rock, ( , )]) # Stop the edit session and commit the changes to the table edit.stopediting(true)

17 Demonstration II Creating a python toolbox Using the data access module to query data

18 Python Add-ins

19 What is an Add-in? An add-in is a customization such as a collection of tools that plugs into ArcGIS Desktop Introduced at 10.0 to make it easier for users to extend ArcGIS Can be authored using.net Language & JAVA (ArcGIS 10.0) ArcGIS 10.1 introduces python to the list of supported languages

20 Python Add-in Wizard Introduced to streamline the add-in creation process Download available from the ArcGIS Resources Center Specify what product it s for Project properties can be defined easily within the wizard Creates all of the directories and files required for the add-in to work

21 Types of Python Add-ins Button Simple click to execute Tool Requires user interaction Combo Box Provide a set of choices Menu Container for buttons or other menus Toolbar Container for every add-in type Tool Palette Container of tools Application Extension Coordinates activities between other components i.e. If an extension is not enabled then the related series of tools will not be enabled

22 File Structure Images contains graphics used in the add-in Install holds the python script where the custom behaviour is stored Config describes the add-in Makeaddin.py utility used to package the files into an add-in

23 Testing / Debugging Add-ins It is important to fully test an add-in before it is shared Steps to conducting a successful test Make the add-in file (run the makeaddin.py) Install the add-in (double click the new add-in file created) Use the add-in In some cases you may not be able to see the custom addin Ensure its been installed (Customize >> Add-in Manager) Debugging Tips and Tricks Use print statements If tools do not load in correctly (i.e. missing on the toolbar) check your python syntax

24 Demonstration III Creating a python add-in

25 Summary In this seminar you were introduced to: 1) Python scripting basics 2) New scripting functionality available in ArcGIS ) Developing python add-ins

26 Resources Using Python Help ArcGIS Python Recipes Related Training Courses Introduction to Geoprocessing Scripts Using Python Follow us: twitter.com/esricanada facebook.com/esricanada