Provide example of widget executing nonblocking code

Summary

Add something like this example to the documentation:

import threading
from IPython.display import display
import ipywidgets as widgets
import time
progress = widgets.FloatProgress(value=0.0, min=0.0, max=1.0)

def work(progress):
    total = 100
    for i in range(total):
        time.sleep(0.2)
        progress.value = (i+1)/total

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

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Original Issue

From what we understand, ipywidgets is a serverextension + nbextension + custom messages that use the shell channel, which blocks on kernel executing code. Is it possible at all, to create a widget that is constantly refreshing its output regardless of whether the kernel’s shell channel is busy or not?

We’d be willing to contribute changes to ipywidgets if you can devise a way to make this possible.

Thanks!

[maartenbreddels]

This example works: https://gist.github.com/maartenbreddels/3378e8257bf0ee18cfcbdacce6e6a77e It also works when you set thread_safe to False, but I know from experience that it will fail sometimes.

[SylvainCorlay]

I think that it is worth creating an example notebook for something like this (and a progress bar) …