Chain Multiselectable Cascading Dropdowns

Dash Python
1

My goal is to chain two multi selectable dropdown callbacks, but I didn’t succeed. Here is, what I tried:

@app.callback(
    Output('merkmal_chosen', 'options'),
    [Input("timeline_chosen", "value"),
    Input('kategorie_chosen', 'value')
    ]   
)

def set_merkmale_options(timeline, kategorie_chosen):
    if timeline == '1':
        df_f = d_bis17[(d_bis17['KATEGORIE'].isin([kategorie_chosen]))]
        return [{'label': l, 'value': l} for l in sorted(df_f['BEZEICHNUNG'].unique())]

    elif timeline == '2':
        df_f = d_ab18[(d_ab18['KATEGORIE'].isin([kategorie_chosen]))]
        return [{'label': l, 'value': l} for l in sorted(df_f['BEZEICHNUNG'].unique())]

If I select a list of elements in first dropdown, nothing ist shown in second chained dropdown.

2

Hello @Toml,

Try running with debug=True in the app.

My guess is that the filtering is operating as a list of lists when you are trying to filter. So, it’s not working the right way.

I’d say, take the ‘kategorie_chosen’ out of the brackets.

3

Hi @jinnyzor,

thanks for the advice. Debug Mode doesn’t show any error messages.

Taking out ‘kategorie_chosen’ from the brackets throws an error, that

only list-like objects are allowed to be passed to isin()

The problem is that both dropdowns should be multi selectable. I have no clue…

4

Can you give an MRE?

Right now, I can’t run it with the code provided. If you provide an MRE, I can make suggestions from there.