[DISCUSSION] Showing figures when running in non-interactive python: to block or not to block?

[wmvanvliet]

@Gnefil pointed out an interesting inconsistency when we are making figures in plain python mode, i.e. when running a script containing visualizations with python myscript.py from the terminal (no ipython or jupyter or anything). The behavior of when a figure window is "blocking" or not is inconsistent among different figure types.

For a concrete example, say we start out script by loading in the evokeds from the MNE-Sample dataset:

import mne
data_path = mne.datasets.sample.data_path()
evokeds_fname = data_path / "MEG" / "sample" / "sample_audvis-ave.fif"
evoked = mne.read_evokeds(evokeds_fname, condition="Left Auditory")

If we continue the script with a topomap figure:

evoked.plot_topomap()

The script will briefly open a window to draw the figure and then close it immediately as the python script terminates. However, if we make it a different kind of plot:

evoked.plot_topo()

The figure window opens and the script blocks execution until the user manually closes the window. If this is not desired, you can disable opening the window entirely with evoked.plot_topo(show=False).

Puzzled by this, I did a search through the codebase on our default blocking behavior and found this:

C:\Users\wmvan\projects\mne-python\mne main
> ag 'plt_show\('
decoding\spatial_filter.py
638:        plt_show(show, block=False)

preprocessing\eyetracking\calibration.py
191:        plt_show(show)

time_frequency\spectrum.py
712:        plt_show(show, fig)
776:        plt_show(show, block=block)

time_frequency\tfr.py
1671:            plt_show(fig=fig)
2171:        plt_show(show)
2467:        plt_show(show)
2598:        plt_show(show)

viz\circle.py
392:    plt_show(show)

viz\epochs.py
402:    plt_show(show)
649:    plt_show(show, fig=fig)
736:    plt_show(show)

viz\evoked.py
207:    plt_show()
569:    plt_show(show)
1734:    plt_show(show)
1794:    plt_show(show)
2071:    plt_show(show)
3230:    plt_show(show)

viz\eyetracking\heatmap.py
208:    plt_show(show)

viz\misc.py
255:    plt_show(show)
374:    plt_show(show)
613:        plt_show(show, fig=fig)
959:    plt_show(show)
1311:    plt_show(show)
1425:    plt_show(show)
1575:    plt_show(show)

viz\ica.py
660:    plt_show(show)
912:    plt_show(show)
1040:    plt_show(show)
1227:    plt_show(show)
1271:    plt_show(show)

viz\_3d.py
410:    plt_show(show)
2303:    plt_show(True)
3236:    plt_show(show)
3656:    plt_show(show)
3993:    plt_show(show, block=block)

viz\utils.py
130:def plt_show(show=True, fig=None, **kwargs):
185:        plt_show(show, block=block, **kwargs)
534:        plt_show(fig=fig_proj, warn=False)
673:            plt_show(fig=fig_help, warn=False)
724:        plt_show(block=True)
762:        plt_show()
1331:    plt_show(show, block=block)

viz\_dipole.py
188:    plt_show(show, block=block)

viz\_proj.py
250:    plt_show(show)

viz\_mpl_figure.py
978:        plt_show(fig=fig)
1042:            plt_show(fig=self.mne.fig_help)
1199:        plt_show(fig=fig)
1767:        plt_show(fig=self.mne.fig_proj, warn=False)

viz\topo.py
423:        plt_show(fig=fig)
1171:    plt_show(show)
1355:    plt_show(show)

viz\topomap.py
524:    plt_show(show)
1485:    plt_show(show)
1881:    plt_show(show)
2111:    plt_show(show)
2282:    plt_show(show, block=False)
3109:        plt_show(show)
3159:    plt_show(show)
3249:    plt_show(True)
3485:    plt_show(show, block=False)
3609:    plt_show(show)
3792:    plt_show(show)
4257:    plt_show(show)

The default matplotlib behavior is to have block=True for plt.show() when in non-interactive mode. But for some reason, we override this setting for some of our plots. We also expose and document the block parameter for our non-matplotlib figures, whereas we don't do this for the matplotlib figures, but that is perhaps besides the point.

Should the hardcoded block=False should be removed from our matplotlib figures that do this? Or is there a good reason why some figures have this?

[Gnefil]

This issue may be relevant to bug #13956.