Hello,
I have an app that takes inputs and runs a long computation (> 10 minutes). The output of this computation is used to populate part of the app.layout. When I run the computation, the app gives me a callback error updating children.
I have tried the techniques for Sharing State Between Callbacks (Link), but they also fail.
Is there a way to get the app to wait for the output before throwing this error?
Here is a small reproducible sample:
import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import State, Input, Output
from dash.exceptions import PreventUpdate
import time
app = dash.Dash(
__name__, meta_tags=[{"name": "viewport", "content": "width=device-width"}]
)
app.layout = html.Div([
html.Button(
"Run",
id="button1",
),
dcc.Slider(
id="slider1",
min=0,
max=10,
step=1,
value=0,
),
dcc.Loading(
id="Loading1",
children=[
html.Div(id="out1", children=[html.P("Nothing yet")]),
],
type="default"
)
])
@app.callback(Output('out1', 'children'),
[Input('button1', 'n_clicks')],
[State('slider1', 'value')])
def update_page(n_clicks, value):
if n_clicks is None:
raise PreventUpdate
else:
time.sleep(100)
out_string = "The output is " + str(value)
return html.P(out_string)
if __name__ == '__main__':
app.run_server(debug=True)
Alternatively, do you think it would be better to have a callback with no output just to trigger the calculation?
Thanks,
Anthony
