# NameError: name 'hv' is not defined

**URL:** <https://discourse.holoviz.org/t/nameerror-name-hv-is-not-defined/8968>\
**Category:** Panel\
**Created:** [October 13, 2025, 5:02am UTC](https://discourse.holoviz.org/t/nameerror-name-hv-is-not-defined/8968 "2025-10-13T05:02:44Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![killcoder](https://discourse.holoviz.org/user_avatar/discourse.holoviz.org/killcoder/32/3236_2.png) [@killcoder](https://discourse.holoviz.org/u/killcoder)\
**Post date:** [October 13, 2025, 5:02am UTC](https://discourse.holoviz.org/t/nameerror-name-hv-is-not-defined/8968/1 "2025-10-13T05:02:44Z")

</div>

My data analytics dashboard(s) throw this error every so often.

```auto
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.

---

<div class="post-metadata">

**Author:** ![Hoxbro](https://discourse.holoviz.org/user_avatar/discourse.holoviz.org/hoxbro/32/3590_2.png) [@Hoxbro](https://discourse.holoviz.org/u/Hoxbro)\
**Post date:** [October 13, 2025, 7:40am UTC](https://discourse.holoviz.org/t/nameerror-name-hv-is-not-defined/8968/2 "2025-10-13T07:40:39Z")

</div>

It looks like you are not `import holoviews as hv` in fuel\_analysis.py.

However, without an MRE, this is likely impossible to determine.

---

<div class="post-metadata">

**Author:** ![killcoder](https://discourse.holoviz.org/user_avatar/discourse.holoviz.org/killcoder/32/3236_2.png) [@killcoder](https://discourse.holoviz.org/u/killcoder)\
**Post date:** [October 13, 2025, 7:54am UTC](https://discourse.holoviz.org/t/nameerror-name-hv-is-not-defined/8968/3 "2025-10-13T07:54:50Z")

</div>

@hoxbro, thanks for the response. Its the very first import on the py file. As I alluded too, the dashboard(s) are up and running but eventually they might crash with this error.

---

<div class="post-metadata">

**Author:** ![Hoxbro](https://discourse.holoviz.org/user_avatar/discourse.holoviz.org/hoxbro/32/3590_2.png) [@Hoxbro](https://discourse.holoviz.org/u/Hoxbro)\
**Post date:** [October 13, 2025, 8:00am UTC](https://discourse.holoviz.org/t/nameerror-name-hv-is-not-defined/8968/4 "2025-10-13T08:00:38Z")

</div>

It could be that you are overwriting `hv` at some point in your code.

Are you running the command with `--dev`?

---

<div class="post-metadata">

**Author:** ![killcoder](https://discourse.holoviz.org/user_avatar/discourse.holoviz.org/killcoder/32/3236_2.png) [@killcoder](https://discourse.holoviz.org/u/killcoder)\
**Post date:** [October 13, 2025, 9:35am UTC](https://discourse.holoviz.org/t/nameerror-name-hv-is-not-defined/8968/5 "2025-10-13T09:35:28Z")

</div>

I do use --dev and --autoreload a lot but in this case I was using --glob to serve up all of my apps