How to replicate "Delete Hierarchy" in Python?

Question

I am trying to do the following using the Python API:

• import an armature from an fbx file
• add it to the asset browser
• delete the armature from the scene, but not from the file, so that I can keep it in the Asset Browser

Fbx import is working nicely and so is adding it to the asset browser. However, when I try to delete the armature from the scene, I only found a way to delete it from the file entirely, which of course removes the armature from the Asset Browser.

However, I noticed that when I don't delete the armature via Python but via right-click on the object in the outliner and then select "delete hierarchy" this fulfills my requirements: The armature is gone from the scene, but it remains in the Asset Browser.

When I manually select Delete instead of Delete hierarchy, the armature is deleted completely from the file as it also happens in my Python approach.

What is different in Delete hierarchy compared to Delete and how can I reproduce this in Python?

Here is my Python approach for Delete hierarchy, which actually deletes "too much":

bpy.ops.object.select_all(action='DESELECT')
bpy.data.objects[fbxArmatureName].select_set(True)
for child in bpy.data.objects[fbxArmatureName].children:
    child.select_set(True)
bpy.ops.object.delete()

Can anyone help me out?

Answer 1

You have to call bpy.ops.outliner.delete(hierarchy=True) using the with keyword with context inside the Outliner. Make sure the Outliner is open in one of the areas in your window.

import bpy

bpy.ops.object.select_all(action='DESELECT')
bpy.data.objects["Armature"].select_set(True)
for child in bpy.data.objects["Armature"].children:
    child.select_set(True)

area_type = 'OUTLINER'
areas  = [area for area in bpy.context.window.screen.areas if area.type == area_type]

if len(areas) <= 0:
    raise Exception(f"Make sure an Area of type {area_type} is open or visible in your screen!")

with bpy.context.temp_override(area=areas[0]):
    bpy.ops.outliner.delete(hierarchy=True)

If you don't have any Outliner open you can switch to Outliner before bpy.ops.outliner.delete(hierarchy=True) is called so you are in the Outliner context.

import bpy

bpy.ops.object.select_all(action='DESELECT')
bpy.data.objects["Armature"].select_set(True)
for child in bpy.data.objects["Armature"].children:
    child.select_set(True)

area_type = 'OUTLINER'
bpy.context.area.ui_type = area_type

with bpy.context.temp_override(area=bpy.context.area):
    bpy.ops.outliner.delete(hierarchy=True)

EDIT UPDATE:

The bpy.ops.outliner.delete function does not function as expected. As mentioned in this thread, the outliner can’t see the new selection until after the script has run.

Outliner operators work on proxy data called tree elements, which is separate from bmain objects. Tree synchronization happens only before the outliner is getting ready to redraw, which will only be at the end of the script. In other words, when you select an object and call bpy.ops.outliner.delete(), the outliner doesn’t know the new selection yet.

One workaround is to use a timer to call the delete operator outside of the main script execution. The timer fires instantly, but still after the script has been executed and the internal outliner tree has been synchronized. The downside is the outliner selection may blip for a split second.

So you need to use a timer as workaround:

import bpy

armature = bpy.data.objects["Armature"]

def select_objects():
    bpy.ops.object.select_all(action='DESELECT')
    armature.select_set(True)
    for child in armature.children:
        child.select_set(True)
    bpy.context.view_layer.objects.active = armature

def delete_objects():
    area_type = 'OUTLINER'
    areas  = [area for area in bpy.context.window.screen.areas if area.type == area_type]

    with bpy.context.temp_override(area=areas[0]):
        bpy.ops.outliner.delete(hierarchy=True)

select_objects()
bpy.app.timers.register(delete_objects, first_interval=0.01)