Plot disappears after executing cell second time

If I have a plot in a notebook cell, and execute it twice, the plot output disappears. This is not what is expected. For example, using this code in one jupyter notebook cell:

%matplotlib widget
import matplotlib.pyplot as plt

and this in another cell:

x = [0, 1, 2, 3]
y = [0, 1, 2, 3]

plt.plot(x, y)

The first time I run this, everything plots fine. But when I execute the second cell twice (or any following calls), the plot disappears. The expected behaviour is that it re-plots (using a different colour). If I then re-run the first cell (with %matplotlib widget), and then the second cell again, it works (but this basically just resets the plot).

If I include a plot command in the first cell, then I can re-run the second cell as many times as I want and it works as expected.

This does not happen if I use %matplotlib inline. I've tested in both jupyter lab and jupyter notebook. My versions are the following:

matplotlib                2.2.2                    py36_1    conda-forge
ipympl                    0.2.1                    py36_0    conda-forge
@jupyter-widgets/jupyterlab-manager
        @jupyter-widgets/jupyterlab-manager v0.35.0  enabled  OK

Commencez par reproduire les deux exemples de cellules de notebook dans JupyterLab et Jupyter Notebook avec les backends widget et inline signalés. Comparez les exécutions répétées de la cellule de tracé et confirmez que le tracé basé sur widget reste visible et est à nouveau rendu comme prévu sans réexécuter la cellule de sélection du backend.