In this chapter, we became familiar with QGIS and the various ways in which it can be used as a Python geospatial development system. We installed and explored the QGIS application itself, and then looked at how Python can be used with QGIS. We saw how QGIS uses data sources, map layers, maps, and projects to organize and work with geospatial data. Next, we examined the three ways in which you can use Python and QGIS: by typing commands into the Python Console, by writing a Python plugin or by writing an external application that makes use of the QGIS Python API.

We then looked at the extensive set of Python libraries that come with QGIS, called PyQGIS, which you can use for geospatial development. We saw how to use the QGIS Python Console to directly manipulate the QGIS project, add layers, zoom in and out, change options, and so on.

Next up, we downloaded and examined a QGIS Python plugin. In doing this, we learned that QGIS plugins are simply Python packages installed in a hidden directory named .qgis2 (or .qgis) within your home or user directory. A plugin makes use of the Qt library to define and build resources such as user interface templates.

Finally, we saw how we can write external Python applications that load the PyQGIS libraries from within the QGIS system, and then use those libraries within a larger PyQt application.

In the next chapter, we will explore the QGIS Python Console in more detail, and use it to become more familiar with the PyQGIS library, and also see how we can use it within our own Python geospatial development projects.