Proposed Updated versions of SO 40165257/8508004 to work in all current Jupyter tech https://stackoverflow.com/a/40165257/8508004

option1_update_forSOexample.py

#For https://stackoverflow.com/a/40165257/8508004
import ipywidgets as widgets
from IPython.display import HTML
w = widgets.Dropdown(
    options=['Addition', 'Multiplication', 'Subtraction', 'Division'],
    value='Addition',
    description='Task:',
)

def on_change(change):
    if change['type'] == 'change' and change['name'] == 'value':
        status_output.update(HTML("changed to %s" % change['new']))

w.observe(on_change)
status_output = display(HTML("STATUS WILL UPDATE HERE"), display_id=True)
display(w)

option2_update_forSOexampleSTAY_WITH_PRINT.py

#For https://stackoverflow.com/a/40165257/8508004
import ipywidgets as widgets
from IPython.display import display
output = widgets.Output()

w = widgets.Dropdown(
    options=['Addition', 'Multiplication', 'Subtraction', 'Division'],
    value='Addition',
    description='Task:',
)

def on_change(change):
    if change['type'] == 'change' and change['name'] == 'value':
        with output:
            output.clear_output() # from 'Output widgets: leveraging Jupyter’s display system' https://ipywidgets.readthedocs.io/en/latest/examples/Output%20Widget.html
            print("changed to %s" % change['new'])

w.observe(on_change)

display(w, output)