Getting the current value of an IPython widget from within a loop

Question

I'd like to get the values of the slider widgets within some loop. However, I would like these to update in real time.

For example see below. In the code pictured, I initialise some sliders, then run the loop below. Whilst the loop is running I move the sliders around. The printed values from the loop do not change from the initial value. When I execute the last cell, the updated slider values are shown.

When you run the for loop cell, the kernel will be busy until the loop is over. I believe that sliding the slider will effectively change w only when the loop cell finishes running. — Fábio Perez
– Fábio Perez, Commented Mar 21, 2018 at 14:14
Thanks Fabio, I saw this but, seeing as I didn't want the loop to wait for input (I'd just like it to check what it is every second) I thought it wasn't relevant. I will check the example again. — James Owers
– James Owers, Commented Mar 21, 2018 at 14:31

James Owers · Accepted Answer · 2018-03-21 14:58:35Z

1

Here's a solution inspired by the last example in asyncronous widgets (as suggested by @Fabio Perez):

import threading
from IPython.display import display
import ipywidgets as widgets
def f(a, b):
    return

w = interactive(f, a=10, b=20)

def work(w):
    for ii in range(10):
        time.sleep(1)
        print(w.kwargs, w.result)

thread = threading.Thread(target=work, args=(w,))
display(w)
thread.start()

This starts a separate thread which checks the values of the widgets.

answered Mar 21, 2018 at 14:58

James Owers

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James Owers Over a year ago

Yes, the whole extensions thing is different for jupyter lab as far as I know

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