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

Creating a simple message dialog

Message dialogs pop up to grab the user's attention and to display important information. In this recipe, we'll create a simple information dialog.

Getting ready

Open the QGIS Python console by going to the Plugins menu and selecting Python Console.

How to do it...

We will create a message dialog and display some text in it, as follows:

  1. First, we need to import the GUI library:

            from PyQt4.QtGui import * 
  2. Then,we'll create the message dialog:

            msg = QMessageBox() 
  3. Next, we'll set the message we want to display:

            msg.setText("This is a simple information message.") 
  4. Finally,we'll call the show method to display the message dialog:


How it works...

Note that we are directly using the underlying Qt framework from which QGIS is built. QGIS API's objects begin with Qgs, while Qt objects begin with just the letter Q.The following screenshot shows the message dialog:

There's more...

A message dialog box should also...