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

Adding a custom shape to the map

The QGIS composer has an object for drawing and styling nonspatial shapes, including rectangles, ellipses, and triangles. In this recipe, we'll add some rectangles filled with different colors, which resemble a simple bar chart, as an example of using shapes.

Getting ready

Download the zipped shapefile for this map from and extract it to your qgis_data directory in a subdirectory named ms.

We will also use the MapComposer library from, to simplify the creation of the map composition.

Place the file in the .qgis2/python directory within your home directory.

How to do it...

First, we will create a simple map composition with the shapefile. Then, we will define the style properties for our rectangles. Next, we will draw the rectangles, apply the symbols, and render the composition. To do this, we need to perform the following steps...