Bokeh hovertools which run arbitrary python code

Question

I am using Bokeh to try and create a figure whose data points when \'hovered\' over by the user will display another graph within the hover tool, showing additional informa

Answer 1

You can use Python callback only in Bokeh server applications. It seems impossible to use Python callbacks for a HoverTool (it must be always a JS callback, or you get this error: ValueError: expected an instance of type Callback, got of type function).

The following solution uses JS callback and it shows a small "tooltip plot" when hovering the circles on the main plot (works for Bokeh v1.0.4 and only if there are 2 plots in the Bokeh document):

from bokeh.plotting import figure, show
from bokeh.layouts import gridplot, Row
from bokeh.models import ColumnDataSource, CDSView, BooleanFilter, CustomJS, BoxSelectTool, HoverTool
import pandas as pd

data = {'x': [1, 2, 3],
        'y':[1, 2, 3],
        'xs':[[9, 8, 7], [6, 5, 4], [3, 2, 1]],
        'ys':[[29, 28, 29], [27, 28, 27], [25, 25, 20]]}
source = ColumnDataSource(data)
plot = figure(title = 'PLOT IN HOVER TOOLTIP', tools = '')
circles = plot.circle('x', 'y', size = 20, source = source)

plot_tooltip = figure(name = 'plot_tooltip', plot_width = 200, plot_height = 200, x_axis_location = None, y_axis_location = None, title = None, tools = 'hover', tooltips = [("x", "@x"), ("y", "@y")], toolbar_location = None)
lines = plot_tooltip.line('x', 'y', source = ColumnDataSource({'x': [], 'y': []}))
circles2 = plot_tooltip.circle('x', 'y', source = ColumnDataSource({'x': [], 'y': []}))

code = """  
var indices = cb_data.index['1d'].indices;
if (indices.length > 0){
    if(plot_tooltip.x_range.bounds == null)
    {
        Bokeh.documents[0].add_root(plot_tooltip)
    }
    const idx = indices[0]
    lines.data_source.data['x'] = source.data['xs'][idx]
    lines.data_source.data['y'] = source.data['ys'][idx]
    lines.data_source.change.emit();

    circles.data_source.data['x'] = source.data['xs'][idx]
    circles.data_source.data['y'] = source.data['ys'][idx]
    circles.data_source.change.emit();  

    div = document.getElementsByClassName('bk-root')[1];
    div.style = "position:absolute; left:" + cb_data.geometry['sx'] + "px; top:" + cb_data.geometry['sy'] + "px;";              
} """

callback = CustomJS(args = dict(source = source, lines = lines, circles = circles2, plot_tooltip = plot_tooltip), code = code)

hover = HoverTool()
hover.callback = callback
hover.tooltips = None
hover.renderers = [circles]
plot.add_tools(hover)

show(plot)

Result: