My input no longer exists but it did before

Dash Python
1

I thought I understood Inputs and callbacks, but every time I think I have it there’s something else lol.

I had this callback that worked great with no errors. It’s on a page called graph.py in a pages directory.

@callback(
    Output('store-results', 'data'),
    Input('save', 'n_clicks'),
    State('store', 'data'),
    State('new-start-date', 'value'),
    State('offset-checkbox', 'value'),
    State('offset-number', 'value'),
    State('lower-bound', 'value'),
    State('upper-bound', 'value'),
    State('selections', 'data')
)
def create_df_from_inputs(
    n1, 
    original_store,  
    new_start_date,
    offset_check,
    offset_custom,
    lower_bound,
    upper_bound,
    events):
    if n1:
        logging.info('Saving Information to POD')
        if original_store['df'] != []:
            df = pd.DataFrame(original_store['df'])
            engine_name = df.iloc[0, 1]
            df['SavGol'] = signal.savgol_filter(df['deviation'], 576, 1)

            if new_start_date is None:
                new_start_date = df.iloc[0, 2]
                logging.info(f'New Start Date: {new_start_date}')

            end_date = df.iloc[-1, 2]
            logging.info(f'End Date: {end_date}')

            offset = 0

            if offset_check:
                offset = df.loc[0, 'SavGol']
                logging.info(f'Offset: {offset}')

            if offset_custom:
                offset = offset_custom
                logging.info(f'Offset: {offset}')


            store = {
                "report": original_store['report'],
                "engine": engine_name,
                "new_start_date": new_start_date,
                "end_date": end_date,
                "offset_value": offset or None,
                "lower_bound": lower_bound or None,
                "upper_bound": upper_bound or None,
                "events": events,
            }
            return store

However I realized I wasn’t gathering the data I intended. So I created a third dcc.Store on my app.py (not in pages) and adjusted the callback to this:

# Save Input Information
@callback(
    Output('store-results', 'data'),
    Input('save', 'n_clicks'),
    State('store', 'data'),
    State('offset-store', 'data'),
    State('new-start-date', 'value'),
    State('lower-bound', 'value'),
    State('upper-bound', 'value'),
    State('selections', 'data'),
)
def create_df_from_inputs(
    n1, 
    original_store,
    offset,  
    new_start_date,
    lower_bound,
    upper_bound,
    events,):
    if n1:
        logging.info('Saving Information to POD')
        if original_store['df'] != []:
            df = pd.DataFrame(original_store['df'])
            engine_name = df.iloc[0, 1]
            df['SavGol'] = signal.savgol_filter(df['deviation'], 576, 1)

            if new_start_date is None:
                new_start_date = df.iloc[0, 2]
            
            logging.info(f'New Start Date: {new_start_date}')

            end_date = df.iloc[-1, 2]
            logging.info(f'End Date: {end_date}')

            # closest = df['date'].searchsorted(f'{new_start_date}T00:00:00')
            # initial_savgol = df['SavGol'].iloc[closest]

            offset_start = 0

            if offset:
                offset_start = offset
                logging.info(f'Offset: {offset_start}')

            store = {
                "report": original_store['report'],
                "engine": engine_name,
                "new_start_date": new_start_date,
                "end_date": end_date,
                "offset_value": offset_start or None,
                "lower_bound": lower_bound or None,
                "upper_bound": upper_bound or None,
                "events": events,
            }
            return store

But now it’s telling me:

A nonexistent object was used in an `Input` of a Dash callback. The id of this object is `new-start-date` and the property is `value`. The string ids in the current layout are: [store, store-results, offset-store, _pages_location, _pages_content, _pages_store, _pages_dummy]

The ‘new-start-date’ is on my graph.py. Ironically another callback is using it just fine.

I’m confused because this callback isn’t in app.py and never was but only decided to throw this error when I included the third store. Any ideas as to why this is happening? Clearly I have a gap in my knowledge about how these all connect otherwise I feel like this shouldn’t be that difficult lol.

2

I moved the dcc.Store to the graph page and it was fine there, but any reason why it wouldn’t work in my app.py?

3

Hello @bpolasek,

When an element gets added to the app or page, I believe it goes through and checks all the things that are registered to update it.

Thus, when it was on the main page, and you didnt have the things to update it, it gave the error. It would have still operated once you went to the graph page.

You can also suppress_callback_exceptions=True in your app spin up to keep this from happening.

1 Like
4

Okay I’ll have to try that next time. Thanks!

1 Like