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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,
+)