Chained callback with 3 dropdowns

I am trying to build a dashboard that will having three dropdowns as input, and upon selection of a value in drop-down1, the options in drop-down 2 and dropdown3 would be filtered to show only corresponding options from the data frame.

I don’t know if this has been implemented, I have seen dependent drop-downs where the first drop down determines the options in the second drop-down.

I want a solution where either of the drop-down can update the value of the other and vice-versa. I am looking forward to your help.

Hi @Lobaloba1

From what you are describing, it sounds essentially the same as the chained callback example in Basic Callbacks | Dash for Python Documentation | Plotly, however, you will need to determine which dropdown triggered the callback.

You can do that using dash.callback_context . You will also need to use dash.no_update so that the triggering dropdown options are not updated.

You can learn more about dash.callback_context and dash.no_update in the “advanced callback” chapter in the dash docs.

Your callback could look something like:

    Output('dropdown-1', 'options'),
    Output('dropdown-2', 'options'),
    Output('dropdown-3', 'options'),
    Input('dropdown-1', 'value'),
    Input('dropdown-2', 'value'),
    Input('dropdown-3', 'value'),    
def update_dropdown_options(value1, value2, value3):
    ctx = dash.callback_context
    input_id = ctx.triggered[0]['prop_id'].split('.')[0]

    if input_id == 'dropdown-1':
        # make new options for dropdown 2 and 3
        # don't update options for dropdown-1
        return dash.no_update, options2, options3
    if input_id == 'dropdown-2':
        # make new options for dropdown 1 and 3
        return options1, dash.no_update, options3
    if input_id == 'dropdown-3':
        # make new option for dropdown 1 and 2
        return options1, options2, dash.no_update

And if this isn’t what you are trying to do, please make a minimal app including some
sample data to demonstrate what you are trying to achieve.


Thanks for this … Would implement and revert

Hello Lobaloba1, were you able to create the solution? What am I looking for for the same implementation?