How can I determine how many vertices/nodes a selected feature has in QGIS 3?
You can use the following script in QGIS Python Editor. Select a layer, run the script and select a feature.
def n_vertices(selected, _, __): n = len(selected) if n == 1: g = iface.activeLayer().selectedFeatures().geometry() print(len([v for v in g.vertices()])) elif n > 1: print("Select only one feature") iface.activeLayer().selectionChanged.connect(n_vertices)
num_points($geometry) returns the number of vertices of the current feature.
Try using the "Identify Features" tool (Ctrl+Shift+I) from the Attributes Toolbar.
Click on the target feature and check the (Derived) tab, where you may see the 'Vertices' attribute