I want the total feature count of all the features in all my layers. Doing it manually in QGIS 2.18.16 is too slow.
I have been trying PyQGIS, but am not good with PyQGIS.
List the vector layers and sum their feature counts:
sum([l.featureCount() for l in iface.mapCanvas().layers() if l.type()==QgsMapLayer.VectorLayer])