Book Image

Mastering Geospatial Development with QGIS 3.x - Third Edition

By : Shammunul Islam, Simon Miles, Kurt Menke, GISP, Richard Smith Jr., GISP, Luigi Pirelli, John Van Hoesen, GISP
Book Image

Mastering Geospatial Development with QGIS 3.x - Third Edition

By: Shammunul Islam, Simon Miles, Kurt Menke, GISP, Richard Smith Jr., GISP, Luigi Pirelli, John Van Hoesen, GISP

Overview of this book

QGIS is an open source solution to GIS and widely used by GIS professionals all over the world. It is the leading alternative to proprietary GIS software. Although QGIS is described as intuitive, it is also, by default, complex. Knowing which tools to use and how to apply them is essential to producing valuable deliverables on time. Starting with a refresher on the QGIS basics and getting you acquainted with the latest QGIS 3.6 updates, this book will take you all the way through to teaching you how to create a spatial database and a GeoPackage. Next, you will learn how to style raster and vector data by choosing and managing different colors. The book will then focus on processing raster and vector data. You will be then taught advanced applications, such as creating and editing vector data. Along with that, you will also learn about the newly updated Processing Toolbox, which will help you develop the advanced data visualizations. The book will then explain to you the graphic modeler, how to create QGIS plugins with PyQGIS, and how to integrate Python analysis scripts with QGIS. By the end of the book, you will understand how to work with all aspects of QGIS and will be ready to use it for any type of GIS work.
Table of Contents (18 chapters)
Title Page
Copyright and Credits
About Packt
Contributors
Preface
Index

Debugging session example


Here, we will show how to debug the TestPlugin remotely. We'll also learn how to insert a code breakpoint, stop executions, and show variable values during executions. The steps to follow are:

  1. Create a PyDev project that points to the source code of TestPlugin
  2. Add a breakpoint to the TestPlugin run() function in the Aptana Debug perspective
  3. Start the PyDev Debug server
  4. Connect to the PyDev server from QGIS
  1. Run the plugin
  2. Explore the variable values
  3. Continue the execution of the plugin

Creating a PyDev project for TestPlugin

To be able to add code breakpoints, it's necessary to load plugin_first.py. This can be simply opened as a file, but it's better to learn how to view the entire plugin as a PyDev project. This allows us to use Aptana as a debug and develop environment. This is done in two steps:

  1. Create a PyDev project in Aptana Studio 3
  2. Link the source code to the project

Creating a PyDev project called plugin_first is done by navigating to File | New Project. This will...