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
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Creating a simple text input dialog


In this recipe, we'll demonstrate one of the simplest methods used for accepting input from a user: a text input dialog.

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 dialog and then configure its title and label. We'll set the editing mode and the default text. When you click on the OK button, the text will be printed to the Python Console. To do this, we need to perform the following steps:

  1. First, we need to import the GUI library:

            from PyQt4.QtGui import * 
    
  2. Next, we initialize the dialog:

            qid = QInputDialog() 
    
  3. Now, we set the window's title, label text, editing mode, and default text:

            title = "Enter Your Name" 
            label = "Name: " 
            mode = QLineEdit.Normal 
            default = "<your name here>" 
    
  4. We configure the dialog while capturing the user input and the return code in...