How to batch merge models with the same prefix in each collection

Question

I have many collections in the scene. There are many models with the same prefix in the collection. I try to merge objects with the same prefix in each collection.

My idea is:

1. Select a collection to hide other collections

---

for i in bpy.data.collections:
    
    i.hide_viewport = True

---

2.Select objects according to prefix. Prefix example 'Assembled','Basic'

for i in bpy.data.collections:

  i.hide_viewport = False

  bpy.ops.object.select_pattern(pattern='Assembled'+"*")

  bpy.ops.object.join() #Warning: Active object is not a selected mesh

  bpy.ops.object.select_all(action='DESELECT')

---

My question is:How do I turn one of the selected objects into an active object In addition, I feel there is something wrong with my thinking. Can I have a simpler solution

Answer 1

You can use a context override

• Loop over all collections
• Gather collection's objects beginning with the prefix
• Join using a context override

.

import bpy

prefix = "Assembler"

for col in bpy.data.collections:
    objects_to_join = [o for o in col.objects if o.name.startswith(prefix)]
    if len(objects_to_join) > 1:  # we don't want to join if there is no object or only one object to join
        bpy.ops.object.join(
            {
                "selected_editable_objects" : objects_to_join,
                "active_object": objects_to_join[0]
            }
        )

Note: this assumes there are only MESH objects which names start with the prefix.