book

ArcPy and ArcGIS: Geospatial Analysis with Python

Name: ArcPy and ArcGIS: Geospatial Analysis with Python
Author: Silas Toms
ISBN: 9781783988662

by Silas Toms

February 2015

Intermediate to advanced

224 pages

4h 57m

English

Packt Publishing

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ArcPy and ArcGIS – Geospatial Analysis with Python
Table of Contents
ArcPy and ArcGIS – Geospatial Analysis with Python
Credits
About the Author
About the Reviewers
www.PacktPub.com
Support files, eBooks, discount offers, and moreWhy subscribe?Free access for Packt account holders
Preface
What this book covers
What you need for this book
Who this book is for

Conventions
Reader feedback
Customer support
Downloading the example codeDownloading the color images of this bookErrataPiracyQuestions
1. Introduction to Python for ArcGIS
Overview of Python
Python as a programming language
Interpreted languageStandard (built-in) libraryThe glue languageWrapper modulesThe basics of PythonImport statementsVariablesFor loopsIf/Elif/Else statementsWhile statementsCommentsData typesStringsIntegersFloatsListsTuplesDictionariesIterable data typesOther important conceptsIndentationFunctionsKeywordsNamespacesZero-based indexing
Important Python Modules for GIS Analysis
The ArcPy moduleThe Operating System (OS) moduleThe Python System (SYS) moduleThe XLRD and XLWT modulesCommonly used built-in functionsCommonly used standard library modules
Summary
2. Configuring the Python Environment
What is a Python script?How Python executes a script
What is the Python interpreter?
Where is the Python interpreter located?Which Python interpreter should be used?How does the computer know where the interpreter is?
Make Python scripts executable when clicked on
Integrated Development Environments (IDEs)
IDLEPythonWinAptana Studio 3IDE summary
Python folder structure
Where modules resideUsing Python's sys module to add a module
The sys.path.append() method
Summary
3. Creating the First Python Script
PrerequisitesModelBuilder
Creating a model and exporting to Python
Modeling the Select and Buffer toolsAdding the Intersect toolTallying the analysis results
Exporting the model and adjusting the script
The automatically generated script
File paths in Python
Continuing the script analysis: the ArcPy tools
The Intersect tool and string manipulationThe string manipulation method 1–string additionThe string manipulation method 2–string formatting #1The string manipulation method 3–string formatting #2
Adjusting the Script
Adding the CSV module to the script
Accessing the data: Using a cursor
The final script
Summary
4. Complex ArcPy Scripts and Generalizing Functions
Python functions–Avoid repeating codeTechnical definition of functionsA first functionFunctions with parametersUsing functions to replace repetitive codeMore generalization of the functions
Summary
5. ArcPy Cursors – Search, Insert, and Update
The data access moduleAttribute field interactionsUpdate cursorsUpdating the shape fieldAdjusting a point locationDeleting a row using an Update CursorUsing an Insert Cursor
Inserting a polyline geometry
Inserting a polygon geometry
Summary
6. Working with ArcPy Geometry Objects
ArcPy geometry object classesArcPy Point objectsArcPy Array objectsArcPy Polyline objectsArcPy Polygon objectsPolygon object buffersOther Polygon object methodsArcPy geometry objectsArcPy PointGeometry objects
Summary
7. Creating a Script Tool
Adding dynamic parameters to a scriptDisplaying script messages using arcpy.AddMessageAdding dynamic components to the script
Creating a Script tool
Labelling and defining parametersAdding data typesAdding the Bus Stop feature class as a parameterAdding the Census Block feature class as a parameterAdding the Census Block field as a parameterAdding the output spreadsheet as a parameterAdding the spreadsheet field names as a parameterAdding the SQL Statement as a parameterAdding the bus stop fields as a parameter
Inspecting the final script
Running the Script Tool
Summary
8. Introduction to ArcPy.Mapping
Using ArcPy with map documents
Inspecting and replacing layer sources
Fixing the broken linksFixing the links of individual layersExporting to PDF from an MXDAdjusting map document elements
Automated map document adjustment
The variablesThe map document object and the text elementsThe layer objectsReplacing the data sourcesAdjusting layer visibilityGenerating a buffer from the bus stops feature classIntersecting the bus stop buffer and census blocksPopulating the selected bus stop and buffer feature classesUpdating the text elementsExporting the adjusted map to PDF
Running the script in the Python Window
Summary
9. More ArcPy.Mapping Techniques
Using arcpy.mapping to control Layer objectsLayer object methods and properties
Definition queries
Controlling the data frame window extent and scale
Adding a Layer objectExporting the maps
Summary
10. Advanced Geometry Object Methods
Creating a Python moduleThe __init__.py file
Adding advanced analysis components
Advanced Polygon object methodsGenerating random points to represent populationUsing the functions within a scriptCreating an XLS using XLWT
Summary
11. Network Analyst and Spatial Analyst with ArcPy
The Network Analyst extension
Using Network Analyst
Creating a Feature DatasetImporting the datasetsCreating the Network DatasetAccessing the Network Dataset using ArcPyBreaking down the script
The Network Analyst module
Accessing the Spatial Analyst Extension
Adding elevation to the bus stopsUsing Map Algebra to generate elevation in feetAdding in the bus stops and getting elevation values
The final result
Summary
12. The End of the Beginning
Getting field information from feature classesAccessing the ListFields' propertiesList comprehensionsCreating the field information functionsQuerying feature class informationGenerating File Geodatabases and feature classesGenerating a feature classSetting up the script tool parametersEnvironmental settingsResolution and tolerance settings
Summary
Index

Content preview from ArcPy and ArcGIS: Geospatial Analysis with Python

The sys.path.append() method

The sys.path function is a list (did you notice the square brackets in the preceding code output?) and as such can be appended or extended to include new file paths that will point to modules the user wants to import. To avoid the need to adjust sys.path, copy the module into the site-packages folder. When this is not possible, use the sys.path.append() method instead:

>>> sys.path.append("C:\\Projects\\Requests")
>>> sys.path
['', 'C:\\WINDOWS\\SYSTEM32\\python27.zip',
  'C:\\Python27\\ArcGIS10.2\\Dells',
  'C:\\Python27\\ArcGIS10.2\\lib',
..'C:\\Python27\\ArcGIS10.2\\lib\\plat-win',
..'C:\\Python27\\ArcGIS10.2\\lib\\lib-tk',
..'C:\\Python27\\ArcGIS10.2\\Lib\\site-packages\\pythonwin',
..'C:\\Python27\\ArcGIS10.2', ...

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ArcPy and ArcGIS: Geospatial Analysis with Python

by Silas Toms

The sys.path.append() method

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