Book Image

QGIS Python Programming Cookbook, Second Edition - Second Edition

By : Joel Lawhead
Book Image

QGIS Python Programming Cookbook, Second Edition - Second Edition

By: Joel Lawhead

Overview of this book

QGIS is a desktop geographic information system that facilitates data viewing, editing, and analysis. Paired with the most efficient scripting language—Python, we can write effective scripts that extend the core functionality of QGIS. Based on version QGIS 2.18, this book will teach you how to write Python code that works with spatial data to automate geoprocessing tasks in QGIS. It will cover topics such as querying and editing vector data and using raster data. You will also learn to create, edit, and optimize a vector layer for faster queries, reproject a vector layer, reduce the number of vertices in a vector layer without losing critical data, and convert a raster to a vector. Following this, you will work through recipes that will help you compose static maps, create heavily customized maps, and add specialized labels and annotations. As well as this, we’ll also share a few tips and tricks based on different aspects of QGIS.
Table of Contents (16 chapters)
QGIS Python Programming Cookbook - Second Edition
About the Author
About the Reviewer
Customer Feedback

Building a custom selection tool

In this recipe, we will build a custom tool that both draws a shape on the map and interacts with other features on the map. These two basic functions are the basis for almost any map tool you would want to build in a standalone QGIS application such as this one or by extending the QGIS desktop application with a plugin.

Getting ready

We will use the application framework from the Adding standard map tools to the canvas recipe, so complete that recipe. We will extend that application with a new tool. The complete version of this application is available in the code samples provided with this book. It will also be beneficial to study the other two tool-related recipes, Using a map tool to draw polygons or lines on the canvas and Using a map tool to draw points on the canvas, as this recipe builds on them as well.

You will also need the following zipped shapefile from

Download and extract...