My data analytics dashboard(s) throw this error every so often.
2025-10-13 10:24:22,323 Exception in callback functools.partial(<bound method IOLoop._discard_future_result of <tornado.platform.asyncio.AsyncIOMainLoop object at 0x000001B736D49D30>>, <Task finished name='Task-6948' coro=<ServerSession.with_document_locked() done, defined at C:\Users\xxxx\test\.venv\Lib\site-packages\bokeh\server\session.py:77> exception=NameError("name 'hv' is not defined")>)
Traceback (most recent call last):
File "C:\Users\xxxx\test\.venv\Lib\site-packages\tornado\ioloop.py", line 758, in _run_callback
ret = callback()
File "C:\Users\xxxx\.venv\Lib\site-packages\tornado\ioloop.py", line 782, in _discard_future_result
future.result()
~~~~~~~~~~~~~^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\bokeh\server\session.py", line 98, in _needs_document_lock_wrapper
result = await result
^^^^^^^^^^^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\panel\reactive.py", line 525, in _change_coroutine
state._handle_exception(e)
~~~~~~~~~~~~~~~~~~~~~~~^^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\panel\io\state.py", line 496, in _handle_exception
raise exception
File "C:\Users\xxxx\test\.venv\Lib\site-packages\panel\reactive.py", line 523, in _change_coroutine
self._change_event(doc)
~~~~~~~~~~~~~~~~~~^^^^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\panel\reactive.py", line 541, in _change_event
self._process_events(events)
~~~~~~~~~~~~~~~~~~~~^^^^^^^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\panel\reactive.py", line 495, in _process_events
raise e
File "C:\Users\xxxx\test\.venv\Lib\site-packages\panel\reactive.py", line 476, in _process_events
self.param.update(**self_params)
~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\param\parameterized.py", line 2406, in update
restore = dict(self_._update(arg, **kwargs))
~~~~~~~~~~~~~^^^^^^^^^^^^^^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\param\parameterized.py", line 2439, in _update
self_._batch_call_watchers()
~~~~~~~~~~~~~~~~~~~~~~~~~~^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\param\parameterized.py", line 2624, in _batch_call_watchers
self_._execute_watcher(watcher, events)
~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\param\parameterized.py", line 2586, in _execute_watcher
watcher.fn(*args, **kwargs)
~~~~~~~~~~^^^^^^^^^^^^^^^^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\panel\param.py", line 569, in link_widget
parameterized.param.update(**{p_name: new})
~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\param\parameterized.py", line 2406, in update
restore = dict(self_._update(arg, **kwargs))
~~~~~~~~~~~~~^^^^^^^^^^^^^^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\param\parameterized.py", line 2439, in _update
self_._batch_call_watchers()
~~~~~~~~~~~~~~~~~~~~~~~~~~^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\param\parameterized.py", line 2624, in _batch_call_watchers
self_._execute_watcher(watcher, events)
~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\param\parameterized.py", line 2586, in _execute_watcher
watcher.fn(*args, **kwargs)
~~~~~~~~~~^^^^^^^^^^^^^^^^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\panel\param.py", line 1070, in update_pane
self._replace_pane()
~~~~~~~~~~~~~~~~~~^^
File "C:\Users\xxxx\test\.venv\Lib\site-packages\panel\param.py", line 930, in _replace_pane
new_object = self.eval(self.object)
File "C:\Users\xxxx\test\.venv\Lib\site-packages\panel\param.py", line 1093, in eval
return eval_function_with_deps(ref)
File "C:\Users\xxxx\test\.venv\Lib\site-packages\param\parameterized.py", line 163, in eval_function_with_deps
return function(*args, **kwargs)
File "C:\Users\xxxx\test\.venv\Lib\site-packages\param\depends.py", line 85, in _depends
return func(*args, **kw)
File "C:\Users\xxxx\test\examples\fuel_analysis.py", line 63, in get_plot
hv.Layout(plots)
^^
NameError: name 'hv' is not defined
At the moment I put it down to long running times of background data refresh or when it has been left running for a while then I come back and change a widget.
Has anyone else come across this error before or does the error report reveal anything to hint at the cause?
Sorry no MRE for this one.
Latest python 3.13, holoviews & panel.