dash python load then update later

Question

I’m somewhat new to dash and python so forgive me and let me know if there’s something that could be simplified or needs to be changed.

Problem

I want to display a number in text and update that number every 10 minutes. I have successfully done this, but the problem is that I want it to load immediately and then update every ten minutes... but then it takes 10 minutes to load this text when the application is first started.

I have a feeling that I need to add a while/if logic for the callback but I’m not sure. Here is a link to the result

See below for the code

If you want it to be reproducible, you can set any number to the data variable within get_data()

#Imports for dash
import dash
from dash.dependencies import Output, Event
import dash_core_components as dcc
import dash_html_components as html

#imports for database connection and data processing
from sshtunnel import SSHTunnelForwarder
import pymysql as db
import pandas as pd


# ssh variables go here
host = 
localhost = 
ssh_username = 
private_key = 
# database variables go here
user=
password=
database=

#This is the function for processing a query
def query(q):
    
    #function for getting data from database

def get_data():
    df_test = query('call example') #calls a procedure which returns a number
    data = df_test['test'].loc[0] # selects the result from the dataframe
    data_insert = 'This month we have {} new clients!!!'.format(data) #inserts the result into the string
    return data_insert

app = dash.Dash(__name__)

app.layout = html.Div(
    [
        html.Div(id='my-div', children='''
        '''.format(get_data())),
        dcc.Interval(
            id='update',
            interval=10* 60000 # I would like for this to be 10 minutes
        )
    ]
)
@app.callback(Output('my-div', 'children'),
              events=[Event('update', 'interval')])
def update_data(): # function for returning the new data
    return get_data()

if __name__ == '__main__':
    app.run_server(debug=True)

Paroofkey Paroofkey · Accepted Answer · 2018-12-13T11:58:00

The Dash community got back to me with a good solution. See below:

from datetime import datetime

import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output


def serve_layout():
    return html.Div(
        [dcc.Interval(id="interval", interval=10000), html.P(id="output")]
    )


app = dash.Dash()

app.layout = serve_layout


@app.callback(Output("output", "children"), [Input("interval", "n_intervals")])
def display_time(n):
    return datetime.now().strftime("The time is: %H:%M:%S")


if __name__ == "__main__":
    app.run_server()

dash python load then update later

Problem

See below for the code

1 Answers