Dynamically link a Span and a Slider in a python bokeh plot

Question

I am trying to create plots in python using bokeh that allow dynamic visualization of data in bins. It's worth knowing that I am relatively new to python, very new to bokeh, and I know ZERO javascript. I have consulted this:

Link a Span or Cursor in between plots with Bokeh in Python

and this:

http://docs.bokeh.org/en/latest/docs/user_guide/interaction/callbacks.html

but am having trouble implementing the necessary parts of each. Here is my code prior to adding the requested capabilities:

from bokeh.layouts import column, widgetbox
from bokeh.models.widgets import Slider
from bokeh.models import Span, CustomJS

output_file('Raw_Spectra_and_Spillover_Data.html')

# widgets for bin setup
Pix1_LowLow = Slider(start = self.StartDAC, end = self.EndDAC, value = 129, step = 1, title = 'Pixel-1 - Low Bin - Low Thresh')
Pix1_LowHigh = Slider(start = self.StartDAC, end = self.EndDAC, value = 204, step = 1, title = 'Pixel-1 - Low Bin - High Thresh')
Pix1_HighLow = Slider(start = self.StartDAC, end = self.EndDAC, value = 218, step = 1, title = 'Pixel-1 - High Bin - Low Thresh')
Pix1_HighHigh = Slider(start = self.StartDAC, end = self.EndDAC, value = 500, step = 1, title = 'Pixel-1 - High Bin - High Thresh')

plot1spect = figure(width=700, height=250, title='pixel-1 Spectrum')
plot1spect.line(self.SpectDACvals1[0], self.SpectrumData1[0], line_width=2)
plot1spect_LowLowSpan = Span(location=Pix1_LowLow.value, dimension = 'height')
plot1spect_LowHighSpan = Span(location=Pix1_LowHigh.value, dimension = 'height')
plot1spect_HighLowSpan = Span(location=Pix1_HighLow.value, dimension = 'height')
plot1spect_HighHighSpan = Span(location=Pix1_HighHigh.value, dimension = 'height')
plot1spect.renderers.extend([plot1spect_LowLowSpan, plot1spect_LowHighSpan, plot1spect_HighLowSpan, plot1spect_HighHighSpan])

plot1spill = figure(width=700, height=250, title='pixel-1 Spillover')
plot1spill.line(self.SpillDACvals1[0], self.SpillData1[0], line_width=2)
plot1spill_LowLowSpan = Span(location=Pix1_LowLow.value, dimension = 'height')
plot1spill_LowHighSpan = Span(location=Pix1_LowHigh.value, dimension = 'height')
plot1spill_HighLowSpan = Span(location=Pix1_HighLow.value, dimension = 'height')
plot1spill_HighHighSpan = Span(location=Pix1_HighHigh.value, dimension = 'height')
plot1spill.renderers.extend([plot1spill_LowLowSpan, plot1spill_LowHighSpan, plot1spill_HighLowSpan, plot1spill_HighHighSpan])

show(row(plot1spect,plot1spill, widgetbox(Pix1_LowLow, Pix1_LowHigh, Pix1_HighLow, Pix1_HighHigh)))

This code gives me this:

If someone can show me how get Pix1_LowLow slider to dynamically control the location of plot1spect_LowLowSpan, then I can extend the technique to the other sliders and spans. Many thanks in advance!

python 3.5.2 - bokeh 12.0

Answer 1

Here is a minimal complete example. Note that the recommended way to add annotations like Span is with plot.add_layout as shown below:

from bokeh.layouts import row, widgetbox
from bokeh.models import Slider, Span, CustomJS
from bokeh.plotting import figure, output_file, show

slider = Slider(start=0, end=10, value=3, step=0.1, title='Slider')

plot = figure(width=700, height=250, x_range=(0,10), y_range=(-1, 1))
span = Span(location=slider.value, dimension='height')
plot.add_layout(span)

callback = CustomJS(args=dict(span=span), code="""
    span.location = cb_obj.value
""")
slider.js_on_change('value', callback)

output_file('span_slider.html')

show(row(plot, widgetbox(slider)))