QGIS will allow you to load a PostgreSQL layer using the QgsDataSourceURI class and QgsVectorLayer (URI, name, provider (Postgres)). For this to work, QGIS needs to be compiled with Postgres support. In this section, you will use psycopg2 as you learned in Chapter 3, Introduction to Geospatial Databases, and Chapter 7, Geoprocessing with Geodatabases. The method of adding features to a layer and a layer to the map in this section will be used later in this chapter when you learn how to write toolboxes.