Euro sign in Bokeh HoverTool

Python 3.10. Bokeh 2.4.3

I have searched and searched but I can’t find a solution.

I’m trying to get a euro sign (€) to appear in a Bokeh HoverTool tooltip. The dollar sign is pretty easy to do:

hover.tooltips = [
        ('Post', '@Post'),
        ('Bedrag', '@Bedrag{$ 0.00}')
    ]

Changing the $ to a € doesn’t do anything.

I’ve tried to somehow use the PrintfTickFormatter with hover.formatters but while the formatter works fine for one of the axis in the figure itself (figVbar.yaxis[0].formatter = PrintfTickFormatter(format="€ %s")), I can’t get it to work with a hovertooltip.

Can someone point me in the right direction?

Answer

One easy modification do get this done is to specify the formatters and use the PrintfTickFormatter in the Hovertool .

The definition of the HoverTool could look like this:

HoverTool(
    tooltips=[
        ('Post', '@Post'),
        ('Bedrag', '@Bedrag{€ %.2f}') # use the format for floats (with 2 digits)
    ],
    formatters={"@Bedrag": "printf"}, # activate the PrintfTickFormatter
)

Minimal Example

from bokeh.plotting import figure, show, output_notebook
from bokeh.models import ColumnDataSource, HoverTool
output_notebook()

source = ColumnDataSource({'index':[0,1,2], 'Post':[1,2,3],'Bedrag':[3,4,5]})

p=figure(width=300, height=300)

bar = p.vbar(x='index', top='Post', source=source, width=0.8)

p.add_tools(
            HoverTool(
                tooltips=[
        ('Post', '@Post'),
        ('Bedrag', '@Bedrag{€ %.2f}')
    ],
        formatters={"@Bedrag": "printf"},
        renderers=[bar],
    )
)

show(p)

Output