Plot is duplicated with repeated calls to plt.show()

[keatonb]

Describe the issue

When I use the "%matplotlib ipympl" backend and display a plot with plt.show(), it works fine, but that plot is displayed again for every future call to plt.show(). The expected behavior is for show() to not repeat the plot output. This occurs with a fresh Anaconda (2024.10-1) installation of Python (3.12.7). This does not happen with default backend.

Versions

 3.12.7 | packaged by Anaconda, Inc. | (main, Oct  4 2024, 08:22:19) [Clang 14.0.6 ]
ipympl version: 0.9.6
Selected Jupyter core packages...
IPython          : 8.30.0
ipykernel        : 6.29.5
ipywidgets       : 8.1.5
jupyter_client   : 8.6.0
jupyter_core     : 5.7.2
jupyter_server   : 2.14.1
jupyterlab       : 4.2.5
nbclient         : 0.8.0
nbconvert        : 7.16.4
nbformat         : 5.10.4
notebook         : 7.2.2
qtconsole        : 5.6.0
traitlets        : 5.14.3
usage: jupyter [-h] [--version] [--config-dir] [--data-dir] [--runtime-dir]
               [--paths] [--json] [--debug]
               [subcommand]

Jupyter: Interactive Computing

positional arguments:
  subcommand     the subcommand to launch

options:
  -h, --help     show this help message and exit
  --version      show the versions of core jupyter packages and exit
  --config-dir   show Jupyter config dir
  --data-dir     show Jupyter data dir
  --runtime-dir  show Jupyter runtime dir
  --paths        show all Jupyter paths. Add --json for machine-readable
                 format.
  --json         output paths as machine-readable json
  --debug        output debug information about paths

Available subcommands: console dejavu events execute kernel kernelspec lab
labextension labhub migrate nbconvert notebook qtconsole run server
troubleshoot trust

Jupyter command `jupyter-nbextension` not found.

I believe that last error is expected for notebook>7, but I'm not certain.

[ianthomas23]

You should not need to call plt.show() when using ipympl. Each Matplotlib Figure that you create (via plt.subplots() or plt.figure() or whatever) is displayed after the code cell in which it is created. Is there a particular reason you are using plt.show()?

[keatonb]

It may not be needed, but it shouldn't hurt. All matplotlib gallery examples end with plt.show(). I can imagine calling imported functions that call show. Expected behavior is for already displayed to no longer be in the show queue, at least to my understanding, and imported function may expect repeated calls to not duplicate already displayed plots? I haven't downgraded things to check, but I don't think this used to happen with ipympl plots in notebook.

[ianthomas23]

I cannot reproduce this, see screenshot:

This is using the same package versions:

Python 3.12.8 | packaged by conda-forge | (main, Dec  5 2024, 14:19:53) [Clang 18.1.8 ] on darwin
ipympl 0.9.6
Selected Jupyter core packages...
IPython          : 8.30.0
ipykernel        : 6.29.5
ipywidgets       : 8.1.5
jupyter_client   : 8.6.0
jupyter_core     : 5.7.2
jupyter_server   : 2.14.1
jupyterlab       : 4.2.5
nbclient         : 0.8.0
nbconvert        : 7.16.4
nbformat         : 5.10.4
notebook         : 7.2.2
qtconsole        : 5.6.0
traitlets        : 5.14.3

and any of matplotlib 3.8.4, 3.9.4 or 3.10.

[keatonb]

There you made a second figure. Here's a screenshot showing what I mean. Without the ipympl magic, no plot would be displayed after the second call to show.