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

Pushing messages to the message bar

The QGIS message bar provides an unobtrusive way to display messages to the user. It displays on the top of the map window on a timer, so it automatically goes away without any required interaction from the user. In this recipe, we'll push a simple message to the status bar.

Getting ready

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

How to do it...

This recipe is a simple one-liner because using the message bar is really easy. We just call the message bar API with a header text message, which will be displayed in bold and another message, which will be displayed without any formatting.

All we do is push two strings to the message bar. The first string will be displayed in bold:

    iface.messageBar().pushInfo(u'Time is running out', u'Read this quickly!') 

How it works...

The message bar lasts for about five seconds and has a button to pause the timer if needed. The message bar is now the primary user communication...