Book Image

Python Geospatial Development - Third Edition

By : Erik Westra
Book Image

Python Geospatial Development - Third Edition

By: Erik Westra

Overview of this book

Geospatial development links your data to locations on the surface of the Earth. Writing geospatial programs involves tasks such as grouping data by location, storing and analyzing large amounts of spatial information, performing complex geospatial calculations, and drawing colorful interactive maps. In order to do this well, you’ll need appropriate tools and techniques, as well as a thorough understanding of geospatial concepts such as map projections, datums, and coordinate systems. This book provides an overview of the major geospatial concepts, data sources, and toolkits. It starts by showing you how to store and access spatial data using Python, how to perform a range of spatial calculations, and how to store spatial data in a database. Further on, the book teaches you how to build your own slippy map interface within a web application, and finishes with the detailed construction of a geospatial data editor using the GeoDjango framework. By the end of this book, you will be able to confidently use Python to write your own geospatial applications ranging from quick, one-off utilities to sophisticated web-based applications using maps and other geospatial data.
Table of Contents (20 chapters)
Python Geospatial Development Third Edition
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

Implementing the DISTAL application


Now that we have the data, we can start to implement the DISTAL application itself. To keep things simple, we will use CGI scripts to implement the user interface.

Tip

What is a CGI Script?

While the details of writing CGI scripts are beyond the scope of this book, the basic concept is to print the raw HTML output to stdout and to process the incoming CGI parameters from the browser using the built-in cgi module.

To run a Python program as a CGI script on Mac OS X or Linux, you have to do two things: first, you have to add a "shebang" line to the start of the script, like this:

#!/usr/bin/python

The exact path you use will depend on where you have Python installed on your computer. The second thing you need to do is make your script executable, like this:

chmod +x selectCountry.py

On MS Windows computers, the file extension (.py) will automatically cause the CGI scripts to call the Python interpreter, so you shouldn't need to do either of these things.

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