divide_hexagons_only.py

# start off in Edit Mode

import bpy
import bmesh

def big_dufus_function():

    obj = bpy.context.edit_object
    me = obj.data

    bm = bmesh.from_edit_mesh(me)

    verts = []
    faces = []

    # get verts
    verts.extend([v.co[:] for v in bm.verts])
    add_vert = verts.append
    add_face = faces.append

    # get new verts and faces
    for f in bm.faces:
        if len(f.verts) == 6:
            add_vert(f.calc_center_median()[:])
            loop = [v.index for v in f.verts]
            loop.append(loop[0])
            for i in range(0,6,2):
                idx1 = loop[i]
                idx2 = loop[i+1]
                idx3 = loop[i+2]
                add_face([idx1, idx2, idx3, len(verts)-1]) 

    # wipe all current bm, and overwrite the Mesh data
    bm.clear()            
    bmesh.update_edit_mesh(me, True)

    bpy.ops.object.mode_set(mode='OBJECT')

    # use obtained new verts and face to do full over-write
    mesh = obj.data
    mesh.from_pydata(verts, [], faces)
    mesh.update()

    bpy.ops.object.mode_set(mode='EDIT')


big_dufus_function()