import bpy
data = {}
for obj in bpy.data.objects: # bpy.context.selected_objects
if obj.type == 'MESH':
data.setdefault(len(obj.data.vertices), []).append(obj)
for key, value in data.items():
group_name = "{} Vertices".format(key)
if group_name not in bpy.data.groups:
bpy.ops.group.create(name=group_name)
grp = bpy.data.groups.get(group_name)
for obj in value:
if len(obj.users_group) == 0:
grp.objects.link(obj)