Annotate 3D scatter plot on pick event

I want to show annotations on a 3D scatter plot when the user clicks on a point.

The code I have shows the annotation once I move the plot after I click on a point.

from mpl_toolkits.mplot3d import proj3d
import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(111, projection = '3d')

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

scatter = ax.scatter(x,y,z,picker=True)

def annotate_onclick(event):

    point_index = int(event.ind)
    print(point_index)

    proj = ax.get_proj()

    x_p, y_p, _ = proj3d.proj_transform(x[point_index], y[point_index], z[point_index], proj)

    plt.annotate(str(point_index), xy=(x_p, y_p))


fig.canvas.mpl_connect('pick_event', annotate_onclick)

plt.show()

How can I make the annotation appear as soon as the user clicks on a point, without having to move the plot?

Answer

Add fig.canvas.draw_idle() at the end of your callback function to force the re-drawing of the new annotation.