ArcPy and ArcGIS geospatial analysis with python by silas toms

ArcPy and ArcGIS – Geospatial Analysis with Python... How does the computer know where the interpreter is?Make Python scripts executable when clicked on Adding the CSV module to the scri

ArcPy and ArcGIS – Geospatial Analysis with Python

ArcPy and ArcGIS – Geospatial Analysis with PythonCredits

About the Author

About the Reviewers

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The XLRD and XLWT modules

Commonly used built-in functions

Commonly used standard library modulesSummary

2 Configuring the Python Environment

What is a Python script?

How Python executes a script

What is the Python interpreter?

Which Python interpreter should be used?

How does the computer know where the interpreter is?Make Python scripts executable when clicked on

Adding the CSV module to the script

The final script

Summary

4 Complex ArcPy Scripts and Generalizing FunctionsPython functions–Avoid repeating code

Labelling and defining parameters

Adding data types

Adding the Bus Stop feature class as a parameterAdding the Census Block feature class as a parameterAdding the Census Block field as a parameter

Adding the output spreadsheet as a parameter

Adding the spreadsheet field names as a parameterAdding the SQL Statement as a parameter

Generating a buffer from the bus stops feature class

Intersecting the bus stop buffer and census blocks

Populating the selected bus stop and buffer feature classesUpdating the text elements

ArcPy and ArcGIS – Geospatial Analysis with Python

ArcPy and ArcGIS – Geospatial Analysis with Python

Copyright © 2015 Packt Publishing

All rights reserved No part of this book may be reproduced, stored in a retrieval system,

or transmitted in any form or by any means, without the prior written permission of thepublisher, except in the case of brief quotations embedded in critical articles or reviews.Every effort has been made in the preparation of this book to ensure the accuracy of theinformation presented However, the information contained in this book is sold withoutwarranty, either express or implied Neither the author, nor Packt Publishing, and its

dealers and distributors will be held liable for any damages caused or alleged to be causeddirectly or indirectly by this book

Silas Toms is a geospatial programmer and analyst with a love of geography, history,

food, and sports He resides in the San Francisco Bay Area and can’t decide which side ofthe Bay is more beautiful He received a bachelor’s degree in Geography from HumboldtState University and is currently pursuing a master’s degree in GIS at San Francisco StateUniversity With a background in GIS analysis for city governments and environmentalconsulting, Silas loves the combination of GIS and Python for analysis automation anddata manipulation

Working for Arini Geographics, Silas is helping governments understand how GIS canorganize and simplify the management of infrastructure and the environment This dualrole as a programmer and analyst allows him to use Python and GIS to quickly producegeospatial data and tools Combined with web mapping, these tools are transforming howgovernments work to serve the public He also teaches workshops on ArcPy and webmapping at the City College of San Francisco, while hoping to one day finish his master’sthesis

Silas has worked as a reviewer on the book Python Geospatial Analysis, Packt Publishing and is working on the book Python Geospatial Development, Packt Publishing to be

published in 2015

I would like to thank my girlfriend, Christine, for her encouragement and patience I

would like to thank my boss, Gabriel Paun, for his inspiration and for pushing me to

become a true GIS professional I would like to thank the faculty at HSU and SFSU fortheir help along the way, and I would like to thank my family for their belief in me and fornever asking me if I was going to become a teacher with my geography degree (eventhough I have and I love it!)

Alessio Di Lorenzo is a marine biologist and has an MSc in Geographical Information

Systems (GIS) and Remote Sensing Since 2006, he has been dealing with the analysis anddevelopment of GIS applications dedicated to the study and spread of environmental andepidemiological data He is experienced in the use of the main proprietary and open sourceGIS software and programming languages

Dara O’Beirne is a certified GIS Professional (GISP) with over eight years of GIS and

Python experience Dara earned both his Bachelors and Masters of Arts degrees in

geography from San Francisco State University Dara is currently a GIS Analyst working

at Arini Geographics in Santa Clara, CA Before joining Arini Geographics, Dara was aGIS Analyst and technical lead at Towill Inc., a GIS and Land Surveying company inNorthern California At Towill, Dara played a central role in developing and implementingprocedures related to the collection and analysis of LiDAR data for environmental andengineering applications Prior to Towill, Dara gained his professional GIS experienceworking for the Golden Gate National Recreation Area managed by the National ParkService, one of the largest urban park systems in the world, which includes National

treasures, such as Alcatraz, Muir Woods, and the Marin Headlands His Master’s Thesisexamined the errors associated with measuring tree heights in an urban environment withboth traditional field methods and airborne LiDAR data

I would like to thank my wife, Kate, and daughter, Anya O’Beirne, for their patience andassistance during the review of this book

Marjorie Roswell is a web developer and map maker from Baltimore, MD She

purchased her first GIS in 1991, and built an application to assist citizen callers to theBaltimore Office of Recycling Recent projects include interactive maps of legislativescores, political endorsements, committees, election data, and advocacy interests

Her site http://committeemaps.org/ details Congressional committee membership, whilethe site http://farmbillprimer.org/ is devoted to mapping and charting federal food andfarm policy

Marjorie is the author of Drupal 5 Views Recipes, Packt Publishing She was the technical reviewer of jQuery UI 1.10, The User Interface Library for jQuery, Packt Publishing.

Mark Pazolli is an engineer and data scientist who uses ArcGIS and Python to help his

employers decipher the mountains of data they keep on the assets of the Western

Australian electrical network He has qualifications in Electrical Engineering, ComputerScience, and Applied Mathematics He appreciates excellent design and enjoys buildinginteresting things

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ArcGIS, the GIS software from industry leader ESRI, allows for the analysis and

presentation of geospatial data

The integration of Python into ArcGIS has made the ArcPy module an important tool forGIS students and professionals The ArcPy module provides a powerful way to improveproductivity when performing geospatial analysis From basic Python scripting throughadvanced ArcPy methods and properties, ArcPy and other Python modules will improvethe speed and repeatability of any GIS work flow

This book will guide you from basic Python scripting to advanced scripting tools Itfocuses on geospatial analysis scripting and touches on automating cartographic output

By the end of this book, you will be able to create reusable modules, add repeatableanalyses as script tools in ArcToolbox, and export maps automatically By reducing thetime-consuming nature of GIS from days to hours, one GIS professional can become aspowerful as a whole team

Chapter 1, Introduction to Python for ArcGIS, offers a quick introduction to the basics ofPython, including other uses for the programming language It covers Python data typesand important modules used throughout the book

Chapter 2, Configuring the Python Environment, is an introduction to how Python works:its folder structure, executables, and modules It also explains importing modules intoscripts, the built-in modules, and covers Integrated Development Environments (IDEs),which are powerful programming aids

Chapter 3, Creating the First Python Script, demonstrates how to use ArcGIS

ModelBuilder to model the first analysis and then export it as a Python script Stringmanipulations and how to use file paths in Python are also introduced

Chapter 4, Complex ArcPy Scripts and Generalizing Functions, examines how to performanalyses and produce outputs that are not possible using ModelBuilder By using

functions, or reusable code blocks, repeating code is avoided

Chapter 5, ArcPy Cursors – Search, Insert, and Update, covers ArcPy data access cursorsand how they are used to search, update, or insert records in feature classes and tables Itexplains the quirks of iterating using cursors, and how to only select or update the records

of interest

Chapter 6, Working with ArcPy Geometry Objects, explores ArcPy Geometry objects andhow they are combined with cursors to perform spatial analysis It demonstrates how tobuffer, clip, reproject, and more using the data cursors and the Arcpy geometry typeswithout using ArcToolbox

Chapter 7, Creating a Script Tool, explains how to make scripts into tools that appear inArcToolbox and are dynamic in nature It explains how the tools and scripts communicateand how to set up the ArcTool dialog to correctly pass parameters to the script

Chapter 8, Introduction to ArcPy.Mapping, explores the powerful Arcpy.Mapping moduleand how to fix broken layer links, turn layers on and off, and dynamically adjust titles andtext It shows how to create dynamic map output based on a geospatial analysis

Chapter 9, More ArcPy.Mapping Techniques, introduces Layer objects, and their methodsand properties It demonstrates how to control map scales and extents for data frames, andcovers automated map export

Chapter 10, Advanced Geometry Object Methods, expands on the ArcPy Geometry objectmethods and properties It also explains how to create a module to save code for reuse insubsequent scripts, and demonstrates how to create Excel spreadsheets containing resultsfrom a geospatial analysis

Chapter 11, Network Analyst and Spatial Analyst with ArcPy, introduces the basics ofusing ArcPy for advanced geospatial analysis using the ArcGIS for Desktop NetworkAnalyst and Spatial Analyst Extensions

understood to have a full grasp of ArcPy These topics include the Environment Settings,

XY values and Z and M resolutions, Spatial Reference Systems (Projections), the Describefunctions, and more

You will need the proprietary or free version of ArcGIS 10.1/10.2/10.3 To support yourenvironment, you will need 2GB RAM, 32-bit or 64 bit machine hardware configuration,and Windows 7/8 Python 2.7 is required to do the programming and is installed alongwith ArcGIS

This book is intended for GIS students and professionals who need an understanding ofhow to use ArcPy to reduce repetitive tasks and perform analysis faster It is also avaluable book for Python programmers who would like to understand how to automategeospatial analysis using the industry standard ArcGIS software and its ArcPy module

In this book, you will find a number of styles of text that distinguish between differentkinds of information Here are some examples of these styles, and an explanation of theirmeaning

Code words in text, database table names, folder names, filenames, file extensions,

pathnames, dummy URLs, user input, and Twitter handles are shown as follows: “The twodata pieces, the BusStopID and the averatePop variable are then added to a list.”

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