Tabulator.from_param fails as soon as the value is changed.

[dejfh]

ALL software version info

Software Version Info

panel   1.8.10
pandas  3.0.1
param   2.3.2
bokeh   3.8.2
python  3.13.5
Ubuntu  24.04.3 LTS (in WSL)

Description of expected behavior and the observed behavior

When I create a Tabulator with Tabulator.from_param, updating the value fails with ValueError.

#8492 introduced a comparison between the current and the new value and expected to result to be a bool (see panel/param.py:575). In this case the values are DataFrames that do not return a bool but another DataFrame (type(pd.DataFrame() != pd.DataFrame()) == pd.DataFrame).

Complete, minimal, self-contained example code that reproduces the issue

import pandas as pd
import panel as pn
import param


class MyObject(param.Parameterized):
    data = param.DataFrame()


my_object = MyObject(data=pd.DataFrame({"a": [1, 2, 3]}))

tabulator = pn.widgets.Tabulator.from_param(my_object.param.data)

tabulator.value = pd.DataFrame({"a": [1, 2, 5]})

Stack traceback and/or browser JavaScript console output

Traceback (most recent call last):
  File "***/test.py", line 14, in <module>
    tabulator.value = pd.DataFrame({"a": [1, 2, 5]})
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "***/.venv/lib/python3.13/site-packages/param/parameterized.py", line 2970, in trigger
    self_.update(dict(params, **triggers))
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "***/.venv/lib/python3.13/site-packages/param/parameterized.py", line 2788, in update
    restore = dict(self_._update(arg, **kwargs))
                   ~~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "***/.venv/lib/python3.13/site-packages/param/parameterized.py", line 2821, in _update
    self_._batch_call_watchers()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "***/.venv/lib/python3.13/site-packages/param/parameterized.py", line 3038, in _batch_call_watchers
    self_._execute_watcher(watcher, events)
    ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "***/.venv/lib/python3.13/site-packages/param/parameterized.py", line 3000, in _execute_watcher
    watcher.fn(*args, **kwargs)
    ~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "***/.venv/lib/python3.13/site-packages/panel/param.py", line 575, in link_widget
    if not reset and current_val != new:
                     ^^^^^^^^^^^^^^^^^^
  File "***/.venv/lib/python3.13/site-packages/pandas/core/generic.py", line 1513, in __bool__
    raise ValueError(
    ...<2 lines>...
    )
ValueError: The truth value of a DataFrame is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

• I may be interested in making a pull request to address this

[zhangdomi]

Hi, I’m interested in working on this. I was able to reproduce the issue and see that it stems from comparing DataFrame values in link_widget. I’ll take a closer look at how best to handle this case without breaking existing behavior.

[github-actions]

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