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

Automatically starting the Python console

As you become familiar with programming QGIS using Python, you'll want the Python console to always be available in QGIS. So, in this recipe, we'll add a Python startup script to QGIS to make sure the console starts when QGIS does.

Getting ready

First, you need the file, which QGIS will read at startup. You'll be able to use this file to customize different aspects of QGIS:

  1. In your user directory, locate the hidden .qgis2 folder.

  2. Your user folder is typically located in ~/.qgis2 on Linux and OSX and C:\Users\<username>\.qgis2 on Windows, which you can also access the %USERPROFILE% environment variable.

  3. Create a Python file named

How to do it...

  1. Open the file you created.

  2. Add the following lines to it:

            from console import console 

How it works...

When QGIS starts, it looks for a Python script named in the user's folder and executes any code it finds there. If you have an error in the file, QGIS will display an error dialog and disable Python within QGIS.