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

Labeling a feature

Once your map layers are styled, the next step to creating a complete map is labeling features. We'll explore the basics of labeling in this recipe.

Getting ready

Download the following zipped shapefile from

Extract the shapefile to a directory named ms in your qgis_datadirectory.

How to do it...

We will load the point shapefile layer, create a label object, set its properties, apply it to the layer, and then add the layer to the map. To do this, we need to perform the following steps:

  1. First, to save space, we'll specify the path to the shapefile:

            src = "/qgis_data/ms/MSCities_Geo_Pts.shp" 
  2. Next, we'll load the layer:

            lyr = QgsVectorLayer(src, "Cities", "ogr") 
  3. Then, we'll create the labeling object:

            label = QgsPalLayerSettings() 
  4. Now, we'll configure the labels, starting with the current layer settings being read: