Given a set of n points in the plane, the Voronoi diagram is a collection of n Voronoi cells, where the ith Voronoi cell defines the region of all points in the plane that lie closest to the ith point given on input. With numpy, scipy, and matplotlib we can conveniently generate and analyze many examples with Python. Counting the vertices and edges of the Voronoi cells, we prove that the total number of vertices and edges of a Voronoi diagram is linear in the number n of input points. This implies that a O(n*log(n)) algorithm to compute a Voronoi diagram is possible. The lecture ends with the characterization of the vertices and the edges of the Voronoi cells.