Jupyter_contrib_nbextensions: Initialization cell displays widgets twice

[codingS3b]

When creating an input cell on a jupyter notebook that displays an ipywidget and marking this cell as Initialization cell, the widget is rendered twice on my machine.

See the following example:

from ipywidgets import widgets
from IPython.display import display

def print_hello(b=None):
    print("hello")

my_button = widgets.Button(description="press it")
my_button.on_click(print_hello)
display(my_button)

However it seems to work correctly when no widgets are involved:

def f(x):
    return x + 3

print(f(5))

Maybe @jcb91 could have a look at this?

Tested with

• firefox 55.0.2
• jupyter 4.3.0
• ipywidgets 6.0.0
• ipython 6.1.0
• jupyter-contrib-nbextensions 0.2.8

[ax3l]

Having the same setup, don't have the problem in the older Firefox ESR 52.3.0 (64-bit) on Debian 9.1 (stretch)

[codingS3b]

Tried again with chromium 60.0.3112.78 running on Ubuntu.16.04 and it seems to be working correctly there as well.

[ax3l]

I downloaded a Firefox 55.0.1 (64bit) for Linux and also can't reproduce it there. Any Firefox Extensions/Plugins you have installed?

[jcb91]

apologies for the delay looking at this @codingS3b. So far, this seems to be working ok for me in Chrome 59.0.3071.115 (Official Build) (64-bit) and FF 55.0.2 (64-bit) on Ubuntu 16.0.4...

[jcb91]

Also, what's your jupyter notebook --version?

[codingS3b]

Concerning plugins I use Adblock Plus but disabled it for testing and the google analytics deactivation add-on but that's it.
My jupyer notebook version is 5.0.0.
I also tried this again using Chromium 60.0.3112.78 on Ubuntu 16.04 and got the same behaviour as with firefox.

I have to add that the widgets are rendered correctly sometimes I refresh the notebook using F5 but sometimes not. Strange thing...

[BarbaraPr]

I have the same problem as codingS3b .. widgets appear twice when executed by an initialization cell

[jcb91]

I'm still unable to reproduce this. Combined with the intermittent observations, this leads me to suspect a timing issue, maybe some race condition somewhere. @BarbaraPr what versions of everything are you running?

Are all of you running the server on the same machine as the browser, or is the notebook server running on a remote machine?

[codingS3b]

I have now tried both versions with firefox and chromium, here are my experiences:

Chromium:

• double rendering happens rarely when running jupyter notebook server on localhost
• when running jupyter notebook server on remote I could not reproduce the issue (refreshing for about 10 minutes now :) )

Firefox:

• double rendering happens quite often when running on localhost
• when running on remote the issue did not come up

Would a screenshot from the browser debugging section help you in some way?

[jcb91]

Thanks @codingS3b, so from that it seems like _maybe_ this issue is more likely to trigger when the notebook is loaded quickly (I asked about local/remote servers because in the past I've found that the extra time required to get the notebook from the remote server can affect timing-related bugs).

Would a screenshot from the browser debugging section help you in some way?

I'm not sure, really :laughing: I'm still at a loss for what could cause this. However, I suspect this has more to do with how widgets are implemented (somehow the cell clearing its outputs on execution is not happening correctly?!) than with init_cell, which after all just queues the cells for regular execution :thinking:

[aseem-hegshetye]

I had same issue when running notebook on ec2 GPU instance.
I had same notebook running on localhost too and synced through dropbox.
so I shutdown the notebook on remote ec2 instance. Then I shut down same notebook on localhost. Then restarted it on ec2 only, and it worked.