What prevents a figure showing before notebook cell completion?

My issue boils down to:

"Why does the figure not show immediately, but instead waits until the cell has completed running?"

%matplotlib widget
import matplotlib.pyplot as plt
from time import sleep
fig = plt.figure()
plt.plot([1,2,3])
sleep(2)

This behaviour is preventing fun uses, like dynamic plotting in a single cell:

%matplotlib widget
from matplotlib import pyplot as plt
from time import sleep
import numpy as np
fig = plt.figure()

for i in range(10):
    x, y = np.random.random(2)
    plt.scatter(x, y)
    fig.canvas.draw()
    sleep(0.1)

The previous code works if one splits it into two cells, placing the figure() call in the first one:

# Cell 1
%matplotlib widget
from matplotlib import pyplot as plt
from time import sleep
import numpy as np
fig = plt.figure()

# Cell 2
for i in range(10):
    x, y = np.random.random(2)
    plt.scatter(x, y)
    fig.canvas.draw()
    sleep(0.1)

Edit: I also note that in the qt backend, there figure and plot are shown immediately, in contrast to the ipympl behaviour.

L’issue ne mentionne aucun fichier source ni aucun test. Commencez par reproduire les exemples avec une seule cellule et avec des cellules séparées à l’aide du backend %matplotlib widget, puis comparez le comportement de fig.canvas.draw() avec le backend Qt ; le travail est considéré comme terminé lorsque la cause et un comportement de rendu approprié sont établis.