On Wed, Jul 10, 2019 at 5:00 PM Ilya Kazakevich
<[email protected]> wrote:
>
> Hello,
>
> According to manual, ``clear_output`` event should clear whole cell output.
>
> But with the following code
>
> from ipywidgets import widgets
> from IPython.display import clear_output
> out = widgets.Output(layout={'border': '1px solid black'})
> out.append_display_data(10)
> display(out)
> display("20")
> out.clear_output()
>
> only "10" is cleared, while "20" stays untouched.
The above behavior is correct, and what I would expect. The reason is
because `out.clear_output()` **only** clears the output of the widget
"out". The "20" that you've output has nothing to do with that output
widget (the one called "out"). The "20" is simply a completely
separate output. To clear everything, which is I think the behavior
you expect, do this, which should work as you want:
from ipywidgets import widgets
from IPython.display import clear_output
out = widgets.Output(layout={'border': '1px solid black'})
out.append_display_data(10)
display(out)
display("20")
clear_output() # NOTICE: I'm calling the global clear_output
function, not the clear_output method of out.
-- William
>
> I sniffed websocket, and I see absolutely regular "clear_output" is sent.
> Then, how does jupyter "understands" that only widget content must be
> cleared? This is not comm message, so no connection to widget is made.
> How does it work?
It's because you type "out.clear_output()" instead of
"clear_output()". This causes a comm message to get sent from the
kernel to the widget saying "clear me". The way out.clear_output
works is a bit surprising, since it involves different back and forth
communication between the kernel and the frontend than you might
expect. This confused me a lot when I was implementing widgets for
CoCalc recently. Search for "clear_output" on this page
https://github.com/jupyter-widgets/ipywidgets/issues/2385#issuecomment-484742927
for where Jason Grout clears up my confusion about how this work...
-- William
>
> Any help (doc or source link probably) is appreciated.
>
> Thank you.
> Ilya.
>
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--
William (http://wstein.org)
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