Simple way to place a label at the top corner of bokeh streaming plots as a python oscilloscope - bokeh

Question

I want to place a label at the top left corner of each streaming plot, be it one plot, or two plots, etc. The plots are stretched in both directions. For now, I have to manually specify a y postion depending on how many plots are shown. (y=200 for two plots, and y=440 for one plot) One may resolve it by recording the total range of y values shown in the plot, but it feels too hacky. I'm wondering if there is a simple way to do this. Thanks for any help.
from bokeh.server.server import Server
from bokeh.models import ColumnDataSource, Label
from bokeh.plotting import figure
from bokeh.layouts import column
import numpy as np
import datetime as dt
from functools import partial
import time
def f_random():
data = np.random.rand()
data = (dt.datetime.now(), data)
return data
def f_sinewave():
data = np.sin(time.time()/1.)
data = (dt.datetime.now(), data)
return data
def make_document(doc, functions, labels):
def update():
for index, func in enumerate(functions):
data = func()
sources[index].stream(new_data=dict(time=[data[0]], data=[data[1]]), rollover=1000)
annotations[index].text = f'{data[1]: .3f}'
sources = [ColumnDataSource(dict(time=[], data=[])) for _ in range(len(functions))]
figs = []
annotations = []
for i in range(len(functions)):
figs.append(figure(x_axis_type='datetime', plot_width=800, plot_height=400, y_axis_label=labels[i]))
figs[i].line(x='time', y='data', source=sources[i])
annotations.append(Label(x=10, y=200, text='', text_font_size='20px', text_color='black',
x_units='screen', y_units='screen', background_fill_color='white'))
figs[i].add_layout(annotations[i])
doc.add_root(column([fig for fig in figs], sizing_mode='stretch_both'))
doc.add_periodic_callback(callback=update, period_milliseconds=100)
if __name__ == '__main__':
# list of functions and labels to feed into the scope
functions = [f_random, f_sinewave]
labels = ['random', 'sinewave']
server = Server({'/': partial(make_document, functions=functions, labels=labels)})
server.start()
server.io_loop.add_callback(server.show, "/")
try:
server.io_loop.start()
except KeyboardInterrupt:
print('keyboard interruption')

Answer 1

For now you could do:
Label(x=10, y=figs[i].plot_height-30, ...)
It seems like allowing negative values to implicitly position against the "opposite" side would be a nice feature (and a good first task for new contributors), so I would encourage you to file a GitHub issue about it.