Remembering selected points in streaming Bokeh plot

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I asked this on StackOverflow here but think maybe this group will be better able to get me to a solution. Here’s my issue:

I want to be able to make a selection (lasso, box_select) of points in a streaming Bokeh scatterplot that will be remembered when the figure updates (e.g., with new data in the time series).

I think this will require me to be able to access the list of the indices of currently selected points, but I can’t figure out how to. Here’s an example where I try (slightly modified from the example at http://bokeh.pydata.org/en/latest/docs/user_guide/server.html#streaming-data-with-the-server). Note that selected points are deselected when the plot updates to the new streamed (shuffled in this example) data.

import time
from random import shuffle
from bokeh.plotting import figure, output_server, cursession, show
# prepare output to server
output_server("remember_selected")

p = figure(plot_width=400, plot_height=400,tools="lasso_select,box_select,help")
p.scatter([1, 2, 3, 4, 5], [6, 7, 2, 4, 5], name='ex_line')
show(p)

# create some simple animation..
# first get our figure example data source
renderer = p.select(dict(name="ex_line"))
ds = renderer[0].
data_source
while True:
    # Update y data of the source object
    shuffle(ds.data["y"])

    #Can I access currently selected points? (NO!)
    print ds.selected['2d']
    print ds.selected['1d']
    print ds.selected['0d']

    # store the updated source on the server
    cursession().store_objects(ds)
    time.sleep(2.)

``

Thanks for any help you can provide!