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

Setting a transparent layer fill

Sometimes, you may just want to display the outline of a polygon in a layer and have the insides of the polygon render transparently, so you can see the other features and background layers inside that space. For example, this technique is common with political boundaries. In this recipe, we will load a polygon layer onto the map, and then interactively change it to just an outline of the polygon.

Getting ready

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

How to do it...

In the following steps, we'll load a vector polygon layer, set up a properties dictionary to define the color and style, apply the properties to the layer's symbol, and repaint the layer. In Python Console, execute the following:

  1. Create the polygon layer:

            lyr = QgsVectorLayer("/qgis_data/ms/mississippi.shp",
                                 "Mississippi", "ogr"...