Using NULL values in PyQGIS

QGIS can use NULL values as field values. Python uses None objects of type None instead of NULL values, which are null memory references. The concepts are similar. You must be aware of this fact when working with Python in QGIS, which is a mixture of C++ and Python. In this recipe, we'll explore the implications of QGIS NULL values in Python.

Getting ready

In your qgis_data/shapes directory, download the following shapefile, which contains some NULL field values, and unzip it:

https://github.com/GeospatialPython/Learn/raw/master/NullExample.zip

How to do it...

We will load the shapefile and grab its first feature. Then, we'll access one of its NULL field values. Next, we'll run through some tests that allow you to see how the NULL values behave in Python:

1. Load the shapefile and access its first feature:

           lyrPth = "/qgis_data/shapes/NullExample.shp" 
           lyr = QgsVectorLayer(lyrPth, "Null Field Example", "ogr&quot...