I've put together a python script to select only the vertex with the minimum z-coordinate from a vertex selection in a mesh. The problem is that it works randomly, resulting in the correct selection only about once in four attempts. Most of the attempts result in none of the vertices getting selected. I've tested it on a square grid of unconnected vertices with neighbour correlated random z-coordinates.
I'm using blender 3.4.1 on MacOS Ventura 13.1
Sample file is here
Tis is the script:
import bpy # Enter Object Mode bpy.ops.object.mode_set(mode='OBJECT') # Get the active mesh mesh = bpy.context.object.data # Get the selected vertices selected_verts = [v for v in mesh.vertices if v.select] # Find the vertex with the minimum z-coordinate min_vert = min(selected_verts, key=lambda v: v.co.z) # Enter Edit Mode bpy.ops.object.mode_set(mode='EDIT') # Deselect all vertices bpy.ops.mesh.select_all(action='DESELECT') # Enter Object Mode bpy.ops.object.mode_set(mode='OBJECT') # Select the min z vertex min_vert.select = True # Enter Edit Mode bpy.ops.object.mode_set(mode='EDIT')