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

Using a filled marker symbol

A newer feature of QGIS is filled marker symbols. Filled marker symbols are powerful features that allow you to use other symbols such as point markers, lines, and shape bursts, as a fill pattern for a polygon. Filled marker symbols allow for an endless set of options for rendering a polygon. In this recipe, we'll do a very simple filled marker symbol that paints a polygon with stars.

Getting ready

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

How to do it...

A filled marker symbol requires us to first create the representative star point marker symbol. Then, we'll add that symbol to the filled marker symbol and change it with the layer's default symbol. Finally, we'll repaint the layer to update the symbology:

  1. First, create the layer with our polygon shapefile:

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