How do I get the return-value of the callback in a periodic callback?

Question

On a bokeh server, I use doc.add_periodic_callback(callback_fn, 1000). This returns the periodic callback ID and nothing else. Is it possible to access the value returned by callback_fn too?

Answer 1

It is not possible to access any return value. This is common for callback-based APIs, since: who/what would receive a return value? The callback is invoked by the system as an automatic process in the background.