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

Changing the QGIS web proxy

QGIS, conveniently, has settings for changing the web proxy it uses to access the Internet. If you are running QGIS on a laptop, you may find yourself changing these settings frequently when you change locations, for example, between work and home or maybe a coffee shop. In this recipe, we'll use PyQGIS to change these settings based on pre-configured options. You can then set a variable name to one of those options, and PyQGIS will change the multiple values needed to alter the proxy.

Getting ready

Open the QGIS Python console by going to the Plugins menu and selecting Python Console.

How to do it...

We will build some dictionary variables for each proxy we want to access. Then, we'll create a variable naming the proxy we want to use. Change the QGIS archived settings, which are accessed when QGIS first launches. Finally, we'll change the settings for the current instance of QGIS so the changes take effect immediately:

  1. First, we import the libraries we need to change...