bokeh server: Is there a way to "manually" sync all models between python and JS

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1

Is there something I can do to force all models to be synced between the JS side and the python side when using a bokeh server?

In a bokeh server app I update a ColumnDataSource with a CustomJS callback, the source data has initially empty columns
This works well and the new data is displayed in the browser.

I also have a python on_change callback for the selected attribute of the source.

The callback triggers when a point is clicked, and the selected indices of the selection are correct, but the source model itself is still empty.

I use 0.12.10, and I understand the selection is now a model and this specific issue might have been fixed.

But I would still like to know if there is a way to do a “manual” general python-JS sync

Thanks

2

Hi,

There is not. Every change you make triggers a change sync event already. It's possible what you are seeing is simply an order of updates issue. If you are looking to simply batch updates in a way that gives you more control, or because you want to coalesce events together, the hold/unhold functions may be useful (I can't quite tell from your description if it will be useful for you or not):

  bokeh.document — Bokeh 3.3.2 Documentation

  https://github.com/bokeh/bokeh/blob/master/examples/howto/hold_app.py

Thanks,

Bryan

···

On Sep 28, 2018, at 08:03, Sébastien Roche <[email protected]> wrote:

Is there something I can do to force all models to be synced between the JS side and the python side when using a bokeh server?

In a bokeh server app I update a ColumnDataSource with a CustomJS callback, the source data has initially empty columns
This works well and the new data is displayed in the browser.
I also have a python on_change callback for the selected attribute of the source.
The callback triggers when a point is clicked, and the selected indices of the selection are correct, but the source model itself is still empty.

I use 0.12.10, and I understand the selection is now a model and this specific issue might have been fixed.
But I would still like to know if there is a way to do a "manual" general python-JS sync

Thanks

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3

Thanks for the answer !

Here is a specific small example:

from bokeh.models import ColumnDataSource, CustomJS, Button
from bokeh.io import curdoc
from bokeh.plotting import figure
from bokeh.layouts import Row

def callback(attr,old,new):
source = curdoc().select_one({‘name’:‘source’})
print source.data

source = ColumnDataSource(data={‘x’:,‘y’:},name=‘source’)

fig = figure(tools=‘tap’)
fig.scatter(‘x’,‘y’,size=10,source=source)

source.on_change(‘selected’,callback)

button = Button(label=‘test’,width=100)

button_code = “”"
var data = source.data;
data[‘x’] = ;
data[‘y’] = ;
for (i=0;i<10;i++){
data[‘x’].push(i);
data[‘y’].push(i);
}
source.change.emit();
“”"

button.callback = CustomJS(args={‘source’:source},code=button_code)

curdoc().add_root(Row(fig,button))

``

After clicking the button the plot is updated with the points

After clicking on a point the terminal output is:
{‘y’: , ‘x’: }

``

4

Oh, in this case it is due to the fact that we cannot detect changes "inside" arrays, and you are only making those kinds of changes. This is an unfortunate JS limitation, I am not aware of anything that can be done about it. The workaround is to set a real, full property, e.g. "source.data = data", which is something the property system can detect:

button_code = """
var data = source.data;
data['x'] = ;
data['y'] = ;
for (i=0;i<10;i++){
data['x'].push(i);
data['y'].push(i);
}
source.data = data;
source.change.emit();
"""

···

On Sep 28, 2018, at 12:02, Sébastien Roche <[email protected]> wrote:

Thanks for the answer !

Here is a specific small example:

from bokeh.models import ColumnDataSource, CustomJS, Button
from bokeh.io import curdoc
from bokeh.plotting import figure
from bokeh.layouts import Row

def callback(attr,old,new):
    source = curdoc().select_one({'name':'source'})
    print source.data

source = ColumnDataSource(data={'x':,'y':},name='source')

fig = figure(tools='tap')
fig.scatter('x','y',size=10,source=source)

source.on_change('selected',callback)

button = Button(label='test',width=100)

button_code = """
var data = source.data;
data['x'] = ;
data['y'] = ;
for (i=0;i<10;i++){
data['x'].push(i);
data['y'].push(i);
}
source.change.emit();
"""

button.callback = CustomJS(args={'source':source},code=button_code)

curdoc().add_root(Row(fig,button))

After clicking the button the plot is updated with the points
After clicking on a point the terminal output is:
{'y': , 'x': }

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5

Hello Bryan,

is there a way to access the event queue before calling “unhold”, e.g. to remove some events from the queue ?

thanks

···

On Friday, September 28, 2018 at 7:05:57 PM UTC+2, Bryan Van de ven wrote:

Hi,

There is not. Every change you make triggers a change sync event already. It’s possible what you are seeing is simply an order of updates issue. If you are looking to simply batch updates in a way that gives you more control, or because you want to coalesce events together, the hold/unhold functions may be useful (I can’t quite tell from your description if it will be useful for you or not):

    [https://bokeh.pydata.org/en/latest/docs/reference/document.html#bokeh.document.document.Document.hold](https://bokeh.pydata.org/en/latest/docs/reference/document.html#bokeh.document.document.Document.hold)



    [https://github.com/bokeh/bokeh/blob/master/examples/howto/hold_app.py](https://github.com/bokeh/bokeh/blob/master/examples/howto/hold_app.py)

Thanks,

Bryan

On Sep 28, 2018, at 08:03, Sébastien Roche [email protected] wrote:

Is there something I can do to force all models to be synced between the JS side and the python side when using a bokeh server?

In a bokeh server app I update a ColumnDataSource with a CustomJS callback, the source data has initially empty columns

This works well and the new data is displayed in the browser.

I also have a python on_change callback for the selected attribute of the source.

The callback triggers when a point is clicked, and the selected indices of the selection are correct, but the source model itself is still empty.

I use 0.12.10, and I understand the selection is now a model and this specific issue might have been fixed.

But I would still like to know if there is a way to do a “manual” general python-JS sync

Thanks

–
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For more options, visit https://groups.google.com/a/continuum.io/d/optout.

6

Hi,

In Python there is always a way. They are in Document._held_events, however I would personally regard mucking with that as a questionable idea. We may for instance change private APIs and attributes at any time with no warning.

Thanks,

Bryan

···

On Sep 29, 2018, at 03:09, chupach <[email protected]> wrote:

Hello Bryan,

is there a way to access the event queue before calling "unhold", e.g. to remove some events from the queue ?

thanks

On Friday, September 28, 2018 at 7:05:57 PM UTC+2, Bryan Van de ven wrote:
Hi,

There is not. Every change you make triggers a change sync event already. It's possible what you are seeing is simply an order of updates issue. If you are looking to simply batch updates in a way that gives you more control, or because you want to coalesce events together, the hold/unhold functions may be useful (I can't quite tell from your description if it will be useful for you or not):

        bokeh.document — Bokeh 3.3.2 Documentation

        https://github.com/bokeh/bokeh/blob/master/examples/howto/hold_app.py

Thanks,

Bryan

> On Sep 28, 2018, at 08:03, Sébastien Roche <[email protected]> wrote:
>
> Is there something I can do to force all models to be synced between the JS side and the python side when using a bokeh server?
>
> In a bokeh server app I update a ColumnDataSource with a CustomJS callback, the source data has initially empty columns
> This works well and the new data is displayed in the browser.
> I also have a python on_change callback for the selected attribute of the source.
> The callback triggers when a point is clicked, and the selected indices of the selection are correct, but the source model itself is still empty.
>
> I use 0.12.10, and I understand the selection is now a model and this specific issue might have been fixed.
> But I would still like to know if there is a way to do a "manual" general python-JS sync
>
> Thanks
>
> --
> You received this message because you are subscribed to the Google Groups "Bokeh Discussion - Public" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to bokeh+un...@continuum.io.
> To post to this group, send email to bo...@continuum.io.
> To view this discussion on the web visit https://groups.google.com/a/continuum.io/d/msgid/bokeh/cbb7b9d1-f174-45d8-a4a5-6b10798adef7%40continuum.io\.
> For more options, visit https://groups.google.com/a/continuum.io/d/optout\.

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