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

Deleting a vector layer feature's attribute

In this recipe, we'll remove an entire attribute and all feature fields for a vector layer. Remember, attributes are the column names and fields are the individual values.

Getting ready

You will need the New York City museums shapefile used in other recipes, which you can download as a ZIP file from the following URL:

Extract this shapefile to /qgis_data/nyc.

How to do it...

This operation is straightforward. We'll load and validate the layer, use the layer data provider to delete the attribute by index, and finally update all of the fields to remove the orphaned values:

  1. Start QGIS.

  2. From the Plugins menu, select Python Console.

  3. First, we load and validate the layer:

            vectorLyr=  QgsVectorLayer('/qgis_data/nyc/NYC_MUSEUMS_GEO.shp',
                                       'Museums' , "ogr") 
  4. Then, we delete the first attribute: