Adding a polygon feature to a vector layer

In this recipe, we'll add a polygon to a layer. A polygon is the most complex kind of geometry; however, in QGIS the API is very similar to a line.

Getting ready

For this recipe, we'll use a simple polygon shapefile which you can download as a ZIP file from the following URL:

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

Extract this shapefile to a folder called polygon in your /qgis_data directory.

How to do it...

This recipe will follow the standard PyQGIS process of loading a layer, building a feature, and adding it to the layer's data provider:

1. Start QGIS.

2. From the Plugins menu, select Python Console.

3. First, load the layer and validate it:

           vectorLyr=  QgsVectorLayer('/qgis_data/polygon/polygon.shp',
                                      'Polyon' , "ogr") 
           vectorLyr.isValid() 
   

4. Next, access the layer's data provider:

           vpr = vectorLyr.dataProvider() 
   

5. Now, we build a list of points for the polygon...