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
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Setting a feature's color using a column in a CSV file

Comma Separated Value (CSV) files are an easy way to store basic geospatial information, but you can also store styling properties alongside the geospatial data for QGIS to use in order to dynamically style the feature data. In this recipe, we'll load some points into QGIS from a CSV file and use one of the columns to determine the color of each point. But note that you can define any property this way.

Getting ready

Download the sample zipped CSV file from the following URL:

Extract it and place it in your qgis_data directory in a directory named shapes.

How to do it...

We'll load the CSV file into QGIS as a vector layer and create a default point symbol. Then we'll specify the property and the CSV column we want to control. Finally, we'll assign the symbol to the layer and add the layer to the map:

  1. First, create the URI string needed to load the CSV:

            uri ...