Getting "ValueError: Lengths must match to compare" when adding more than 2 or more options in dropdown

📊 Plotly Python
1

I am getting that ValueError when trying to use the dropdown with multiple selections (having 1 default value works fine); having two or more values results in the value error.

app.layout = html.Div([
    html.H1(
        children = "Visualizing Daily Occupancy Numbers at",
        style = {'textAlign': 'center'}
    ),

    # What the user clicks on 
    dcc.Dropdown(
        id="select_sector",
        options=list(dict(label=sector, value=sector) for sector in list(df['sector'].unique())),
        value= 'Co-ed',
        multi=True
    ),

    html.Div(id='output_container', children=[]),
    html.Br(),
    dcc.Graph(id='my_line_graph', figure={}) # input graph type
])

# ------------------------------------------------------------------------------------------
# CONNECT THE PLOTLY GRAPHS WITH DASH COMPONENTS 
@app.callback(
    [Output(component_id='output_container', component_property='children'),
    Output(component_id='my_line_graph', component_property='figure')],
    [Input(component_id='select_sector', component_property='value')]
)
def update_graph(option_selected): # refers to Input component property value (^above)
    print(option_selected)
    print(type(option_selected))

    container = "The sector chosen by the user was: {}".format(option_selected)

    dff = df.copy()
    dff = dff[dff['sector'] == option_selected]

    # Plotly Express
    fig = px.line(
        data_frame=dff,
        x='occupancy_date',
        y='occupancy'
    )

    return container,fig ```
2

Hi!
I had the same error and I have written an article to circumvent this error.
You can check it: https://shraddhashekhar.medium.com/valueerror-lengths-must-match-to-compare-when-adding-more-than-2-options-in-dropdown-3b4e0a5c77d4