Can anyone explain this dcc.Store error message?


I am confused by this error message. I have watched the Sharing Information Between Callbacks many times. and I thought I followed the directions to the letter. I am especially confused by this particular error message because the dcc.Store component is supposed to accept lists as valid data, according to the documentation cited below.

I printed out the data and it is a list of dictionaries.

Can anyone explain what is wrong and what to do about it?

Thank you,


1. Documentation:

data ( dict | list | number | string | boolean ; optional): The stored data for the id.

2. dcc.Store component

dcc.Store(id=‘store-data’, data= , storage_type=‘memory’, clear_data=False)

The idea here was to contain the data in the data_key and and clear it after every session by changing the clear_data value to True when the session ends, triggered by the production of the final report.

3. Here is the callback:

The user approves a datatable of information - an intermediary step that allows the user to edit and approve the data to be analyzed, after the initial processing, but before the final analysis. The approved data is then stored in dcc.Store.

If I comment out the callback, the rest of the code functions fine.

    Output('store-data', 'data'),
    Input('nutrients-review-datatable-submit-button', 'n_clicks'),
def store_approved_data(n_clicks):
    if n_clicks > 0:

        with open("./json/edited_recipe_data.json", "r") as data_store:
            data = json.loads(

            return data.to_dict('records')

4. Here is the error message:

I printed out the data and it is one list of dictionaries. I have also - out of desperation - tried to use a for loop to return each dictionary inside the list, which did not work. No big surprise there.

Hi @robertpfaff

The error is saying that you are trying to send a “list” object into the Dash Table in the line 200 of store_approved_data file.

Add an if statement before that line to be sure the “data” is not a list.

1 Like

It is strange, though, because line 200 is not in the store_approved_data function. It is part of another callback/function entirely that returns the final analysis using dbc.Table.from_dataframe. I’ve had no problems with it until now, and its data source is definitely not a list - but a dataframe. Both callbacks share an Input, however, and that must be the source of the problem. Thank you for clarifying the issue.