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USING PYTHON IN ARCGIS: A REPORT FROM THE REAL WORLD

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I <3 Python!

STEVE SHAFFER

Also ArcGIS

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You can find me at:

sshaffer@eecenvironmental.com

steve.shaffer.ninja

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NOW YOUR TURN

  1. Who uses ArcGIS?

Desktop / Pro / Server / Online

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  • Who uses Geoprocessing?

GP Tools / ModelBuilder / arcpy / ArcObjects

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  • Who uses Python?

Desktop / Web / ArcGIS

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  • Who uses/used VBA?

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SOME BACKGROUND

on ArcGIS, Python, and arcpy

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1

GETTING SETUP

First things first

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INSTALL PYTHON

  • Install from Esri
    • Installs to C:\Pythonxx\ArcGISxx.x

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OR

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  • Install from Somewhere Else
    • Installs to C:\Pythonxx\
    • Need to separately install the arcpy site package

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GET A PYTHON CODE EDITOR

  • If you’ve never done this before, you will be tempted to skip this step and just use Notepad.

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  • Don’t.

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THE CODE EDITOR SPECTRUM

Text Editor

“IDE”

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Integrated Development Environment

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WHICH ONE TO CHOOSE?

Here, try a list on Python’s site!

https://wiki.python.org/moin/PythonEditors

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hahahahahaha...

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THAT DIDN’T HELP

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MY RECOMMENDATION: PYCHARM

  • Free community edition
  • Cross-platform

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  • Code completion
  • Jump to definition
  • Inspections
  • Auto save
  • VCS integration
  • So much more!

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  • Can be overwhelming at first

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CONFIGURE IDE INTEGRATION

  • Set IDE as editor

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  • Configure IDE to recognize *.pyt files as Python
    • If using .pyt
    • See next slide

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  • Configure IDE to use the correct Python interpreter
    • If applicable
    • See next++ slide

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  • Configure IDE to recognize *.pyt files as Python

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  • Configure IDE to use the correct Python interpreter

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(per-project setting)

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2

WRITING SCRIPTS

Live by the code

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BASIC SCRIPT STRUCTURE

import arcpy #Package imports

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map_path = arcpy.GetParameterAsText(0) #Process parameters

pdf_path = arcpy.GetParameterAsText(1)

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map = arcpy.mapping.MapDocument(map_path) #Do stuff

arcpy.mapping.ExportToPDF(map, pdf_path)

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arcpy.AddMessage(‘Finished exporting’) #Log it!

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del map #Clean up

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BASIC SCRIPT STRUCTURE (STANDARD PYTHON WAY)

import arcpy #Package imports

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def main():

map_path = arcpy.GetParameterAsText(0) #Process parameters

pdf_path = arcpy.GetParameterAsText(1)

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map = arcpy.mapping.MapDocument(map_path) #Do stuff

arcpy.mapping.ExportToPDF(map, pdf_path)

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arcpy.AddMessage(‘Finished exporting’) #Log it!

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del map #Clean up

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if __name__ == “__main__”:

main() #Kick it off!

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3

DEPLOYING SCRIPTS

> gis push

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ADD SCRIPT TO TOOLBOX

Given a script and a toolbox…

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  1. Toolbox > Right-click > Add > Script

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  • Use wizard / properties to define…
    1. Name, alias, etc.
    2. Parameters: make sure they match up with your code!
    3. Validation: separate Python code
    4. Help: go ahead and link to your .chm...

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  • Use your script wherever you use GP tools!

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WORKFLOW: STANDARD TOOLBOX

add to UI

write script

.py

GP Tool

Button

add to model

add to AGS

GP Service

add to toolbox

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WORKFLOW: PYTHON TOOLBOX

add to UI

write toolbox

.pyt

Button

add to model

add to AGS

GP Service

GP Tools

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STANDARD TOOLBOX VS. PYTHON TOOLBOX

Standard Toolbox

  • Scripts live next to other tools�
  • Configuration is defined through GUI�
  • Edit script and configuration in different places�
  • Can embed source code�
  • OK for version control

Python Toolbox

  • Only Python tools in toolbox�
  • Everything is code��
  • Edit everything in one place��
  • Supports licensing�
  • Version control friendly

Full comparison from Esri

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DEMOS!

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Add buttons to ArcMap

Replace your old VBA scripts!

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ADD BUTTONS TO ARCMAP

Given a GP tool...

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  1. Enter “customize mode” in ArcMap

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  • “Commands” tab > [Geoprocessing Tools] < {your script}

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Automate Map Creation and Publication

Replace DS Map Book!

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AUTOMATE MAP CREATION AND PUBLICATION

arcpy.mapping.____________

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Some Classes:

MapDocument, LegendElement, DataFrame, TextElement, ImageElement, DataDrivenPages, ...

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Some Methods:

AddLayer(), UpdateLayer(), RemoveLayer(), ...

ListDataFrames(), ListLayers(), ...

ListBrokenDataSources()

ExportToPDF(), ExportToAI(), PrintMap(), ...

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Create Geographic Data from Tables

Replace humans!

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CREATE GEOGRAPHIC DATA FROM TABLES

Reading data: arcpy.SearchCursor

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Editing data: arcpy.UpdateCursor

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Writing data: arcpy.InsertCursor

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CURSORS

import arcpy�from arcpy import env��# Set the workspace�env.workspace = "D:/St_Johns/data.gdb"��# Create the search cursor�cur = arcpy.SearchCursor("roads", '"TYPE" <> 4')��# Iterate through the rows in the cursor�for row in cur:� print "Name: %s, CFCC code: %s" % (row.NAME, row.CFCC)�

# Deallocate the cursor objects�del cur, row

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Build Complex Geoprocessing Models

Replace ModelBuilder!

(the annoying parts)

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BUILD COMPLEX GEOPROCESSING MODELS

ModelBuilder is still great for composing tools.

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A best practice: write small, generic tools in Python and compose them, along with other GP tools in ModelBuilder

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Build ArcGIS Server Geoprocessing Services

Replace third-party software???

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BUILD ARCGIS SERVER GEOPROCESSING SERVICES

A geoprocessing service is just a GP tool that you expose as a service in ArcGIS Server.

It doesn’t even really have to be geographic.

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Could use Python to build a custom printing service!

(but I haven’t yet)

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PYTHON IN ARCGIS PRO?

<Insert wisdom here>