DeprecationWarning: Passing unrecognized arguments to super(Toolbar).__init__().

[Firestar-Reimu]

Describe the issue

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
File ~/.miniforge/lib/python3.13/site-packages/traitlets/traitlets.py:1379, in HasTraits.__init__(self, *args, **kwargs)
   1378 try:
-> [1379](https://file+.vscode-resource.vscode-cdn.net/home/firestar/NAOC/HVC-catalog/Test/~/.miniforge/lib/python3.13/site-packages/traitlets/traitlets.py:1379)     super().__init__(*super_args, **super_kwargs)
   1380 except TypeError as e:

TypeError: NavigationToolbar2WebAgg.__init__() missing 1 required positional argument: 'canvas'

During handling of the above exception, another exception occurred:

DeprecationWarning                        Traceback (most recent call last)
Cell In[24], [line 4](vscode-notebook-cell:?execution_count=24&line=4)
      2 cluster_id = hvc_candidates[i]
      3 moment_0_crop, extent, xc, yc, a, b, theta, area = cluster_params[i]
----> [4](vscode-notebook-cell:?execution_count=24&line=4) fig, ax = plt.subplots(1, 2, figsize=[10, 4])
      5 im = ax[0].imshow(
      6     moment_0_crop,
      7     extent=extent,
   (...)     10     interpolation="none",
     11 )
     12 cs = ax[0].contour(
     13     moment_0_crop,
     14     levels=[0.5 * np.max(moment_0_crop)],
   (...)     18     linestyles="solid",
     19 )

File ~/.miniforge/lib/python3.13/site-packages/matplotlib/pyplot.py:1776, in subplots(nrows, ncols, sharex, sharey, squeeze, width_ratios, height_ratios, subplot_kw, gridspec_kw, **fig_kw)
   1621 def subplots(
   1622     nrows: int = 1, ncols: int = 1, *,
   1623     sharex: bool | Literal["none", "all", "row", "col"] = False,
   (...)   1630     **fig_kw
   1631 ) -> tuple[Figure, Any]:
   1632     """
   1633     Create a figure and a set of subplots.
   1634 
   (...)   1774 
   1775     """
-> [1776](https://file+.vscode-resource.vscode-cdn.net/home/firestar/NAOC/HVC-catalog/Test/~/.miniforge/lib/python3.13/site-packages/matplotlib/pyplot.py:1776)     fig = figure(**fig_kw)
   1777     axs = fig.subplots(nrows=nrows, ncols=ncols, sharex=sharex, sharey=sharey,
   1778                        squeeze=squeeze, subplot_kw=subplot_kw,
   1779                        gridspec_kw=gridspec_kw, height_ratios=height_ratios,
   1780                        width_ratios=width_ratios)
   1781     return fig, axs

File ~/.miniforge/lib/python3.13/site-packages/matplotlib/pyplot.py:1041, in figure(num, figsize, dpi, facecolor, edgecolor, frameon, FigureClass, clear, **kwargs)
   1031 if len(allnums) == max_open_warning >= 1:
   1032     _api.warn_external(
   1033         f"More than {max_open_warning} figures have been opened. "
   1034         f"Figures created through the pyplot interface "
   (...)   1038         f"Consider using `matplotlib.pyplot.close()`.",
   1039         RuntimeWarning)
-> [1041](https://file+.vscode-resource.vscode-cdn.net/home/firestar/NAOC/HVC-catalog/Test/~/.miniforge/lib/python3.13/site-packages/matplotlib/pyplot.py:1041) manager = new_figure_manager(
   1042     num, figsize=figsize, dpi=dpi,
   1043     facecolor=facecolor, edgecolor=edgecolor, frameon=frameon,
   1044     FigureClass=FigureClass, **kwargs)
   1045 fig = manager.canvas.figure
   1046 if fig_label:

File ~/.miniforge/lib/python3.13/site-packages/matplotlib/pyplot.py:551, in new_figure_manager(*args, **kwargs)
    549 """Create a new figure manager instance."""
    550 _warn_if_gui_out_of_main_thread()
--> [551](https://file+.vscode-resource.vscode-cdn.net/home/firestar/NAOC/HVC-catalog/Test/~/.miniforge/lib/python3.13/site-packages/matplotlib/pyplot.py:551) return _get_backend_mod().new_figure_manager(*args, **kwargs)

File ~/.miniforge/lib/python3.13/site-packages/matplotlib/backend_bases.py:3504, in _Backend.new_figure_manager(cls, num, *args, **kwargs)
   3502 fig_cls = kwargs.pop('FigureClass', Figure)
   3503 fig = fig_cls(*args, **kwargs)
-> [3504](https://file+.vscode-resource.vscode-cdn.net/home/firestar/NAOC/HVC-catalog/Test/~/.miniforge/lib/python3.13/site-packages/matplotlib/backend_bases.py:3504) return cls.new_figure_manager_given_figure(num, fig)

File ~/.miniforge/lib/python3.13/site-packages/ipympl/backend_nbagg.py:430, in _Backend_ipympl.new_figure_manager_given_figure(num, figure)
    428 if 'nbagg.transparent' in rcParams and rcParams['nbagg.transparent']:
    429     figure.patch.set_alpha(0)
--> [430](https://file+.vscode-resource.vscode-cdn.net/home/firestar/NAOC/HVC-catalog/Test/~/.miniforge/lib/python3.13/site-packages/ipympl/backend_nbagg.py:430) manager = FigureManager(canvas, num)
    432 if is_interactive():
    433     _Backend_ipympl._to_show.append(figure)

File ~/.miniforge/lib/python3.13/site-packages/ipympl/backend_nbagg.py:402, in FigureManager.__init__(self, canvas, num)
    400 FigureManagerWebAgg.__init__(self, canvas, num)
    401 self.web_sockets = [self.canvas]
--> [402](https://file+.vscode-resource.vscode-cdn.net/home/firestar/NAOC/HVC-catalog/Test/~/.miniforge/lib/python3.13/site-packages/ipympl/backend_nbagg.py:402) self.toolbar = Toolbar(self.canvas)

File ~/.miniforge/lib/python3.13/site-packages/ipympl/backend_nbagg.py:126, in Toolbar.__init__(self, canvas, *args, **kwargs)
    125 def __init__(self, canvas, *args, **kwargs):
--> [126](https://file+.vscode-resource.vscode-cdn.net/home/firestar/NAOC/HVC-catalog/Test/~/.miniforge/lib/python3.13/site-packages/ipympl/backend_nbagg.py:126)     DOMWidget.__init__(self, *args, **kwargs)
    127     NavigationToolbar2WebAgg.__init__(self, canvas, *args, **kwargs)
    129     self.on_msg(self.canvas._handle_message)

File ~/.miniforge/lib/python3.13/site-packages/ipywidgets/widgets/widget.py:503, in Widget.__init__(self, **kwargs)
    501 """Public constructor"""
    502 self._model_id = kwargs.pop('model_id', None)
--> [503](https://file+.vscode-resource.vscode-cdn.net/home/firestar/NAOC/HVC-catalog/Test/~/.miniforge/lib/python3.13/site-packages/ipywidgets/widgets/widget.py:503) super().__init__(**kwargs)
    505 Widget._call_widget_constructed(self)
    506 self.open()

File ~/.miniforge/lib/python3.13/site-packages/traitlets/traitlets.py:1385, in HasTraits.__init__(self, *args, **kwargs)
   1383     arg_s_list.append(f"{k}={v!r}")
   1384 arg_s = ", ".join(arg_s_list)
-> [1385](https://file+.vscode-resource.vscode-cdn.net/home/firestar/NAOC/HVC-catalog/Test/~/.miniforge/lib/python3.13/site-packages/traitlets/traitlets.py:1385) warn(
   1386     "Passing unrecognized arguments to super({classname}).__init__({arg_s}).\n"
   1387     "{error}\n"
   1388     "This is deprecated in traitlets 4.2."
   1389     "This error will be raised in a future release of traitlets.".format(
   1390         arg_s=arg_s,
   1391         classname=self.__class__.__name__,
   1392         error=e,
   1393     ),
   1394     DeprecationWarning,
   1395     stacklevel=2,
   1396 )

File ~/.miniforge/lib/python3.13/site-packages/traitlets/utils/warnings.py:14, in warn(msg, category, stacklevel, source)
      9 def warn(msg: str, category: t.Any, *, stacklevel: int, source: t.Any = None) -> None:
     10     """Like warnings.warn(), but category and stacklevel are required.
     11 
     12     You pretty much never want the default stacklevel of 1, so this helps
     13     encourage setting it explicitly."""
---> [14](https://file+.vscode-resource.vscode-cdn.net/home/firestar/NAOC/HVC-catalog/Test/~/.miniforge/lib/python3.13/site-packages/traitlets/utils/warnings.py:14)     warnings.warn(msg, category=category, stacklevel=stacklevel, source=source)

DeprecationWarning: Passing unrecognized arguments to super(Toolbar).__init__().
NavigationToolbar2WebAgg.__init__() missing 1 required positional argument: 'canvas'
This is deprecated in traitlets 4.2.This error will be raised in a future release of traitlets.

Versions

 3.13.11 | packaged by conda-forge | (main, Dec  6 2025, 11:24:03) [GCC 14.3.0]
ipympl version: 0.9.8
Selected Jupyter core packages...
IPython          : 9.8.0
ipykernel        : 7.1.0
ipywidgets       : 8.1.8
jupyter_client   : 8.7.0
jupyter_core     : 5.9.1
jupyter_server   : 2.17.0
jupyterlab       : not installed
nbclient         : 0.10.4
nbconvert        : 7.16.6
nbformat         : 5.10.4
notebook         : not installed
qtconsole        : not installed
traitlets        : 5.14.3

[Firestar-Reimu-Pro]

I does not know why this problem happen nor can I re-create the problem, this is like ghost

I only know this happen when fig, ax = plt.subplots(1, 2, figsize=[10, 4])

[rossjjennings]

I've run into this too and just wasted a couple of hours trying to chase it down, which was very annoying. It would show up a few cells into a big notebook, and then in every plot cell thereafter, but seemingly go away if I tried to start fresh to get a minimal example. But it might just be that the warning is getting suppressed somehow. Using a warnings filter to convert warnings into errors, I get it more reliably. This seems to be sufficient to reproduce it:

import numpy as np
import matplotlib.pyplot as plt

%matplotlib widget

import warnings
with warnings.catch_warnings():
    warnings.simplefilter('error')
    plt.figure()

Relevant versions for me are:

matplotlib = 3.10.8
ipympl = 0.9.8
ipywidgets = 8.1.8
traitlets = 5.14.3

My understanding of what happens (given the traceback after converting to an error) is that constructing a Figure eventually calls ipympl.backend_nbagg._Backend_ipympl.new_figure_manager_given_figure(), which tries to construct a FigureManager, which in turn tries to construct a Toolbar. The constructor for ipympl.backend_nbagg.Toolbar gets passed a canvas object, but its base class matplotlib.backends.backend_webagg_core.NavigationToolbar2WebAgg doesn't get it on the other end.

The class Toolbar inherits from both ipywidgets.widgets.domwidget.DOMWidget and matplotlib.backends.backend_webagg_core.NavigationToolbar2WebAgg, giving it a pretty big MRO to dig through:

>>> ipympl.backend_nbagg.Toolbar.__mro__
(ipympl.backend_nbagg.Toolbar,
 ipywidgets.widgets.domwidget.DOMWidget,
 ipywidgets.widgets.widget.Widget,
 ipywidgets.widgets.widget.LoggingHasTraits,
 traitlets.traitlets.HasTraits,
 traitlets.traitlets.HasDescriptors,
 matplotlib.backends.backend_webagg_core.NavigationToolbar2WebAgg,
 matplotlib.backend_bases.NavigationToolbar2,
 object)

Interesting things seem to be happening in the constructors for:

• ipywidgets.widgets.widget.Widget (passes along **kwargs but not *args, which is where the canvas object should be)
• traitlets.traitlets.HasTraits (This is what gives rise to the warning, which would otherwise be an error. The canvas is already gone at this point).

[rossjjennings]

Update: I eventually figured out that this warning is normally hidden, and the only reason it showed up at all was part of my own code that called warnings.resetwarnings() after changing the warnings filter. Updating that code to use a with warnings.catch_warnings() block got rid of the warning, but presumably the underlying cause is still there.

[Firestar-Reimu-Pro]

Why is traitlets 5.14 now but ipympl is still using a pre-4.2 function