The dual graph of a Voronoi diagram is a Delaunay Triangulation:
(The corners of the Voronoi polygons are the circumcenters of Delaunay triangles, and the seed points of the Voronoi diagram are the vertices of Delaunay triangles. Corresponding edges of the two diagrams are perpendicular)
This relationship is so key that many libraries/algorithms for ...
Try randomly checking "will this item drop?" for every item. You could store the information for item and drop chance as pairs in a list:
drops = [["sword",5],["hp_potion",35],["mp_potion",35]]
loot = 
for i in drops:
...but this does not ...