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QGIS Python Programming Cookbook

You're reading from   QGIS Python Programming Cookbook Over 140 recipes to help you turn QGIS from a desktop GIS tool into a powerful automated geospatial framework

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Product type Paperback
Published in Mar 2015
Publisher
ISBN-13 9781783984985
Length 340 pages
Edition 1st Edition
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Author (1):
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Joel Lawhead Joel Lawhead
Author Profile Icon Joel Lawhead
Joel Lawhead
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Table of Contents (11) Chapters Close

Preface 1. Automating QGIS FREE CHAPTER 2. Querying Vector Data 3. Editing Vector Data 4. Using Raster Data 5. Creating Dynamic Maps 6. Composing Static Maps 7. Interacting with the User 8. QGIS Workflows 9. Other Tips and Tricks Index

Changing a vector layer feature's attribute


The process to change an attribute in a feature is straightforward and well-supported by the PyQGIS API. In this recipe, we'll change a single attribute, but you can change as many attributes of a feature as desired at once.

Getting ready

You will need the New York City museums' shapefile used in other recipes, which you can download as a ZIP file from https://geospatialpython.googlecode.com/svn/NYC_MUSEUMS_GEO.zip.

Extract this shapefile to /qgis_data/nyc.

How to do it...

We will load the shapefile as a vector layer, validate it, define the feature IDs of the fields we want to change, get the index of the field names that we will change, define the new attribute value as an attribute index and value, and change the feature in the layer. To do this, we need to perform the following steps:

  1. Start QGIS.

  2. From the Plugins menu, select Python Console.

  3. First, load the layer and validate it:

    vectorLyr =  QgsVectorLayer('/qgis_data/nyc/NYC_MUSEUMS_GEO.shp', 'Museums...
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