plot - How to add HoverTool to a Data Table (Bokeh, Python)

Question

I am experimenting with bokeh data table. Is it possible to add HoverTool to each field in bokeh table?

An example of DataTable-

And and example of how HoverTool works-

Answer 1

This is possible using HTMLTemplateFormatter:

main.py:

from os.path import dirname, join
import pandas as pd
from bokeh.io import curdoc, show
from bokeh.models import ColumnDataSource, Div
from bokeh.models.widgets import DataTable, TableColumn, HTMLTemplateFormatter
from bokeh.layouts import layout

template = """<span href="#" data-toggle="tooltip" title="<%= value %>"><%= value %></span>"""

df = pd.DataFrame([
    ['this is a longer text that needs a tooltip, because otherwise we do not see the whole text', 'this is a short text'],
    ['this is another loooooooooooooooong text that needs a tooltip', 'not much here'],
], columns=['a', 'b'])

columns = [TableColumn(field=c, title=c, width=20, formatter=HTMLTemplateFormatter(template=template)) for c in ['a', 'b']]

table = DataTable(source=ColumnDataSource(df), columns=columns)

l = layout([[table]])

curdoc().add_root(l)

show(l)

A slightly nicer way (though a bit more painful) would use a different template with some CSS styling.

template = """<div class="tooltip-parent"><div class="tooltipped"><%= value %></div><div class="tooltip-text"><%= value %></div></div>"""

desc.html:

<style>
.tooltip-parent {
    width: 100%;
}

.tooltipped {
    overflow: hidden;
    width: 100%;
}

.tooltip-text {
    visibility: hidden;
    width: 250px;
    background-color: rgba(0, 0, 0, 1);
    color: #fff;
    text-align: center;
    border-radius: 6px;
    padding: 5px 5px;
    position: relative;
    z-index: 1;
    top: 100%;
    left: 0%;
    white-space: initial;
    text-align: left;
}

.tooltipped:hover + .tooltip-text {
    visibility: visible;
}

div.bk-slick-cell {
    overflow: visible !important;
    z-index: auto !important;
}
</style>

<h1>Tooltip demo</h1>