Need to create and update figures in seperate cells?

Something I’ve seen in previous versions as well as the current version: In order to have a figure that dynamically updates while some code is executing (e.g. tracking the loss function of an optimization), I have to create the figure in a separate jupyter notebook cell and run it before a I run the code that updates. If I don’t do this, then a blank figure shows and never updates. I’m using Jupyter lab. Wondering if I’m doing something wrong here? It would make the code cleaner and easier to run if it could all be put in a single cell.

Example:

Using the following function:

def update_function(fig, ax):
   while True:
       # Do some computation
       ax.clear() #clear previously drawn
       ax.plot(some_data)
       fig.canvas.draw() #force it to update

This works:

# cell 1
fig, ax = plt.subplots()

# cell 2
update_function(fig, ax)

But this does not:

# one combined cell
fig, ax = plt.subplots()
update_function(fig, ax)

[ianhi]

as an aside I would recommend instead of clearing and redrawing every time you should use the set_data methods. e.g

line = ax.plot(some_data)[0]

# for updating
line.set_data(new_data)
fig.canvas.draw()

[ianhi]

ahh and it turns out that there is a pretty simple workaround for the meantime

%matplotlib widget
from matplotlib import pyplot as plt
from time import sleep
import numpy as np

def display_immediately(fig):
    canvas = fig.canvas
    display(canvas)
    canvas._handle_message(canvas, {'type': 'send_image_mode'}, [])
    canvas._handle_message(canvas, {'type':'refresh'}, [])
    canvas._handle_message(canvas,{'type': 'initialized'},[])
    canvas._handle_message(canvas,{'type': 'draw'},[])
    
    
with plt.ioff():
    fig = plt.figure()

display_immediately(fig)

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