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

Adding standard map tools to the canvas

In this recipe, you'll learn how to add standard map navigation tools to a standalone map canvas. Creating the simplest possible interactive application provides a framework to begin building specialized geospatial applications using QGIS as a library.

Getting ready

Download the following zipped shapefile and extract it to your qgis_data directory into a folder named ms from

How to do it...

We will walk you through the steps required to create a map canvas, add a layer to it, and then add some tools to zoom and pan the map, which are given as follows:

  1. First, because we are working outside the QGIS Python interpreter, we need to import some QGIS and Qt libraries:

            from qgis.gui import * 
            from qgis.core import * 
            from PyQt4.QtGui import * 
            from PyQt4.QtCore import SIGNAL, Qt 
            import sys, os 
  2. Then, we must set the location of...