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"""
The message bus system can be used to receive notifications when properties of
Blender datablocks are changed via the data API.
Limitations
-----------
The message bus system is triggered by updates via the RNA system. This means
that the following updates will result in a notification on the message bus:
- Changes via the Python API, for example ``some_object.location.x += 3``.
- Changes via the sliders, fields, and buttons in the user interface.
The following updates do **not** trigger message bus notifications:
- Moving objects in the 3D Viewport.
- Changes performed by the animation system.
Example Use
-----------
Below is an example of subscription to changes in the active object's location.
"""
import bpy
# Any Python object can act as the subscription's owner.
owner = object()
subscribe_to = bpy.context.object.location
def msgbus_callback(*args):
# This will print:
# Something changed! (1, 2, 3)
print("Something changed!", args)
bpy.msgbus.subscribe_rna(
key=subscribe_to,
owner=owner,
args=(1, 2, 3),
notify=msgbus_callback,
)
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