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

Stepping the user through a wizard

A wizard is a series of dialogs that lead the user through a sequence of steps. The information on each page of a wizard might relate in some way to the information on other pages. In this recipe, we'll create a simple three-page wizard to collect some information from the user and display it back to them.

Getting ready

Open the QGIS Python console by selecting the Plugins menu and then clicking on Python Console.

How to do it...

We will create three classes, each representing a page of our wizard. The first two pages will collect information, and the third page will display it back to the user. We will create a QWizard object to tie the page classes together. We will also use the concept of wizard fields to pass information among the pages. To do this, we need to perform the following steps:

  1. First, we import the GUI and QGIS core libraries:

            from PyQt4.QtCore import * 
            from PyQt4.QtGui import * 
  2. Next, we create the class for the first...