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

Creating a combobox

A combobox provides a drop-down list to limit the user's selection to a defined set of choices. In this recipe, we'll create a simple combobox.

Getting ready

Open the QGIS Python console by selecting the Plugins menu and then clicking on Python Console.

How to do it...

In this recipe, we will initialize the combobox widget, add choices to it, resize it, display it, and then capture the user input in a variable for printing to the console. To do this, we need to perform the following steps:

  1. First, we import the GUI library:

            from PyQt4.QtGui import * 
  2. Now, we create our combobox object:

            cb = QComboBox() 
  3. Next, we add the items that we want the user to choose from:

            cb.addItems(["North", "South", "West", "East"]) 
  4. Then, we resize the widget:

  5. Now, we can display the widget to the user:

  6. Next, choose an item from the list to change it from the default.

  7. Finally, we print the choice to the console...