Problem with dcc.Store in plotly dash - each clalback input value as None

Dash Python
1

Hi,

I’m trying to build some dashboard which will show me some real time data from live experiment. I had it worked, but once I’ve tried to upgrade it, it is not working anymore. Here is the idea of my code

app.layout = html.Div([
    ...
    dcc.Store(id='time'),
    dcc.Store(id='old_data'),
	...
	
	html.Div([
        dcc.Graph(id='figure1'),
        dcc.Interval(
            id='interval-component',
            interval=1*1000, # in milliseconds
            n_intervals=0
        )
    ])
])

@callback([Output('old_data', 'data'),
            Output('time', 'data'),]
          Input('interval-component', 'n_intervals'),
          [State('time', 'data'),
           State('data', 'data')]
              )
def update_graph_live(n,time1,prev_data):
    
    if time1 is None:
        time=0
        prev_data = pd.to_json(pd.DataFrame({}))
    else:
        
        a= pd.read_sql('SELECT * FROM test_data where Time >', time1, conn)
        prev_data1 = a+prev_data
        prev_data = pd.to_json()
        time = time1+1

    return prev_data, time

The problem is that each time the callback is executed, the time1 value is getting None value. Please assist me to solve the problem for this.

2

Are you referring to a change of the dash version?

4

No change in dash version