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Archived discussions · Captured October 28, 2026

RangeSlider raises a DeserializationError error when changing the value

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roinr
roinr

OS: WSL
Python: 3.7
Bokeh: 2.3.1

I have the following dashboard:

from bokeh.io import curdoc
from bokeh.models.widgets.sliders import RangeSlider

rs = RangeSlider(start=0, end=5, value=(0, 5))


def on_change(attr, old, new):
    print("value changed")


rs.on_change("value", on_change)
curdoc().add_root(rs)

When I try to change the value (using the UI) I get the following error:

bokeh.core.property.bases.DeserializationError: Tuple(Float, Float) expected a list, got [1, 5]
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_jm
_jm

Hi @roinr

I created an Anaconda environment with python 3.7 and bokeh 2.3.1, and cannot reproduce your error.

The slider initializes the (start,end) extrema and initial values properly. When the slider is manipulated, the callback prints the message and the slider updates as expected.

This also works as expected in my default Anaconda environment with python 3.9 and bokeh 2.3.2.

My operating system is OSX Big Sur.

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