Enabling Multi-Select in ipython-widgets

Question

I have a development problem. I need to be able to select multiple items at the same time from a drop-down menu in python using ipython-widgets. So far, I have been able to choose an option a single-option widget menu, which upon selection will plot its corresponding statistics. I have pasted my code below, and I would greatly appreciate it if you could help me out.

import numpy as np
import pandas as pd
import ipywidgets as widgets
import matplotlib.pyplot as plt
import panel as pn
pn.extension()


classes= widgets.Dropdown(
description='Products:',
options= list(output_table.class_m.unique())
)


start_year = widgets.BoundedFloatText(
    value=output_table.year.min(),
    min=output_table.year.min(),
    max=output_table.year.max(),
    step=1,
    description='Start Year:',
    disabled=False,
    color='black'
)
end_year = widgets.BoundedFloatText(
    value=output_table.year.max(),
    min=output_table.year.min(),
    max=output_table.year.max(),
    step=1,
    description='End Year:',
    disabled=False,
    color='black'
)


output=widgets.Output()

def response(name, start, end):
    name = classes.value
    output.clear_output()
    df2 = output_table.copy()
   # Filter between min and max years (inclusive)
    df2 = df2[(df2.year >= start) & (df2.year <= end)]
    with output:
        if len(df2) > 0:
            plot1 = df2[df2['class_m'] == name].groupby(['month']).agg({'units':'sum'}).reset_index()
            plot1.plot(x='month', y='units')
            clear_output(wait=True)
            plt.show()
        else:
            print("No data to show for current selection")
def event_handler(change):
    response(change.new, start_year.value, end_year.value)

def start_year_handler(change):
    response(classes.value, change.new, end_year.value)

def end_year_handler(change):
    response(classes.value, start_year.value, change.new)

classes.observe(event_handler, names='value')
start_year.observe(start_year_handler, names = 'value')
end_year.observe(end_year_handler, names = 'value')

display(classes)
display(start_year)
display(end_year)

Answer 1

Have a look at the SelectMultiple widget (https://ipywidgets.readthedocs.io/en/stable/examples/Widget%20List.html#SelectMultiple).

w = widgets.SelectMultiple(
    options=['Apples', 'Oranges', 'Pears'],
    value=['Oranges'],
    #rows=10,
    description='Fruits',
    disabled=False
)

You can shift-click to choose multiple selections, then call w.value to get the list of selected values.