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

Navigating to a map bookmark

Map bookmarks store important locations on a map, so you can quickly find them later. You can programmatically navigate to bookmarks using the Python sqlite3 library in order to access the bookmarks database table in the QGIS user database and then using the PyQGIS canvas API.

Getting ready

We will use a census tract layer to test out the bookmark navigation. You can download the zipped shapefile from

Manually load this layer into QGIS after extracting it from the ZIP file. Also, make sure that you have completed the previous recipe, Creating a map bookmark. You will need a bookmark named BSL for an area of interest in this shapefile.

How to do it...

We will retrieve a bookmark from the QGIS user database and then set the map's extents to this bookmark. To do this, perform the following steps:

  1. First, import the Python sqlite3 library:

            import sqlite3 
  2. Next, get the location of the...