How Do I Create A Loading Indicator In Bokeh?

I am using a radio button with Bokeh. I want to be able to show a loading indicator when a radio button is clicked and then show that it has finished after the python callback has

Solution 1:

Assuming the user already have a plot in view one option would be to set a callback on the start attribute of the plot's range so it will be triggered when the plot gets updated.

from bokeh.models import CustomJS

p = figure()

defpython_callback()
    p.y_range = Range1d(None, None)
    # get your data here and update the plot

code = "document.getElementById('message_display').innerHTML = 'loading finished';"
callback = CustomJS(args = dict(), code = code)
p.y_range.js_on_change('start', callback)

See working example below:

import numpy as np
from bokeh.plotting import figure, show
from bokeh.models import CustomJS, ColumnDataSource

points = np.random.rand(50, 2)
cds = ColumnDataSource(data = dict(x = points[:, 0], y = points[:, 1]))

p = figure(x_range = (0, 1), y_range = (0, 1))
p.scatter(x = 'x', y = 'y', source = cds)

cb_to_make_selection = CustomJS(args = {'cds': cds}, code = """
function getRandomInt(max){return Math.floor(Math.random() * Math.floor(max));}
cds.selected.indices = [getRandomInt(cds.get_length()-1)]
""")

p.x_range.js_on_change('start', cb_to_make_selection)

show(p)