Python - Blender Get selected Object in order of Selection

Question

I'm wondering if there a way to get an object selection in order of selection. It' seams that Blender sort objects by keys, but the selection order is important for my tool.

Is there a way to do that ? I found many topic on other forum from 2015, I'm wondering if now we could do this ?

EDIT : A bit of Context :

1. I have 4 Attributes on each objects ( marking front / back / right / left )
2. I want to compare 2 objects together, see if the Right Attribute match the Left Attribute of the other Object
3. I want my first selection to be the Object you compare too At the end I'm returning :
4. Object 1 Front value == Object 2 Back Value
5. Object 1 Back value == Object 2 Front Value
6. Object 1 Right value == Object 2 Left Value
7. Object 1 Left value == Object 2 Right Value

the result is the same if I compare the first to the second or the second to the first, it's just more user friendly to know My first selection is the base and the second is the one I compare to the first.

Answer 1

Use get_ordered_selection_objects()

import bpy

def get_ordered_selection_objects():
    tagged_objects = []
    for o in bpy.data.objects:
        order_index = o.get("selection_order", -1)
        if order_index >= 0:
            tagged_objects.append((order_index, o))
    tagged_objects = sorted(tagged_objects, key=lambda item: item[0])
    return [o for i, o in tagged_objects]

def clear_order_flag(obj):
    try:
        del obj["selection_order"]
    except KeyError:
        pass

def update_selection_order():
    if not bpy.context.selected_objects:
        for o in bpy.data.objects:
            clear_order_flag(o)
        return
    selection_order = get_ordered_selection_objects()
    idx = 0
    for o in selection_order:
        if not o.select_get():
            selection_order.remove(o)
            clear_order_flag(o)
        else:
            o["selection_order"] = idx
            idx += 1
    for o in bpy.context.selected_objects:
        if o not in selection_order:
            o["selection_order"] = len(selection_order)
            selection_order.append(o)

def selection_change_handler(scene):
    if bpy.context.mode != "OBJECT":
        return
    is_selection_update = any(
        not u.is_updated_geometry
        and not u.is_updated_transform
        and not u.is_updated_shading
        for u in bpy.context.view_layer.depsgraph.updates
    )
    if is_selection_update:
        update_selection_order()

def register():
    bpy.app.handlers.depsgraph_update_post.append(selection_change_handler)

if __name__ == "__main__":    
    for f in bpy.app.handlers.depsgraph_update_post:
        if f.__name__ == "selection_change_handler":
            bpy.app.handlers.depsgraph_update_post.remove(f)
    register()