@app,callback created python compile error

Dash Python
1

Hi, total newbie. I am struggling with how to have my dashboard automatically update. I have a very simple dashboard, at this time, jsut a H3 displaying the system date/time.

import dash
import dash_core_components as dcc
import dash_html_components as html
import dash_bootstrap_components as dbc
from dash.dependencies import Input, Output
import plotly.graph_objs as go

#Setup for Dash
external_stylesheets = [dbc.themes.SIMPLEX]
app = dash.Dash(name, external_stylesheets=external_stylesheets)
app.title=“Weather Station”

colors = {
‘background’: ‘#000000’,
‘bodyColor’: ‘#00000’,
‘text’: ‘#FFFFFF’,
‘red’: ‘#FF0800’
}

dt_time = datetime.now()
print (dt_time)
app.layout = html.Div([
#html.H3(children=[display_dow, " - - ", display_date, " - - ", display_time],
html.H3(children=["Hello ", dt_time],

        id="head1",
               style={
                   'textAlign': 'center',
                   'backgroundColor': colors['red'],
                   'color': colors['text']
                   }),
        dcc.Interval(
            id='interval-component',
            interval=1*1000,
            n_intervals=0)
    ])

@app.callback(Output(‘head1’,‘children’),
Input(‘interval-component’,‘n-intervals’))

print(“Hello world”)
if name == ‘main’:
app.run_server(debug=False)

I added the Print(“Hello world”) simply to ensure I had no error in the that is erroring out.

Whenever I run the program, I get an error on the line immediately after the @app.callback

%Run simple_dashboard.py
Traceback (most recent call last):
File “/home/pi/Desktop/simple_dashboard.py”, line 46
print(“Hello world”)
^
SyntaxError: invalid syntax

I believe I am using the correct format for the @app.callback, but as I mentioned, no matter what I have after this, results in an error.

If I comment out the 2 lines for the app.callback, the dasboard renders properly.

Any thoughts would be appreciated.

If it helps understand my purpose, I am trying to develop a dashboad for my weather station. All my readings are published to a MQTT server (Pubnub) and I want a dashboard which subscribes to the channel and displays the results. I am able to subscribe to Pubnub, create a dashboard and manually refresh the browser (running on a Raspberry PI4), all that’s left is to automatically refresh the data once a minute (either on timer or on subscribe results),

Thanks

2

Hi @scaseley, welcome to the community!

Your code is hard to read, click the code icon of the editor and paste your code inside the highlighted section.

image
image1610×102 7.41 KB

If you want your dashboard to be updated automatically you can use the dcc.Interval component. More info here - Live Updates | Dash for Python Documentation | Plotly.

3 
#!/usr/bin/python
#Setup for PUBNUB subscribe

from datetime import datetime
import dash
import dash_core_components as dcc
import dash_html_components as html
import dash_bootstrap_components as dbc
from dash.dependencies import Input, Output
import plotly.graph_objs as go

#Setup for Dash
external_stylesheets = [dbc.themes.SIMPLEX]
app = dash.Dash(__name__, external_stylesheets=external_stylesheets)
app.title="Weather Station"

colors = {
    'background': '#000000',
    'bodyColor': '#00000',
    'text': '#FFFFFF',
    'red': '#FF0800'
    }

dt_time = datetime.now()
print (dt_time)
app.layout = html.Div([
            #html.H3(children=[display_dow, " - - ", display_date, " - - ", display_time],
            html.H3(children=["Hello ", dt_time],
            
            id="head1",
                   style={
                       'textAlign': 'center',
                       'backgroundColor': colors['red'],
                       'color': colors['text']
                       }),
            dcc.Interval(
                id='interval-component',
                interval=1*1000,
                n_intervals=0)
        ])

@app.callback(Output('head1','children'),
              Input('interval-component','n-intervals'))
                  

print("Hello world")
if __name__ == '__main__': 
    app.run_server(debug=False)
4

Hi @scaseley

Your decorator needs a function after the input and output:

@app.callback(Output('head1','children'),
              Input('interval-component','n-intervals'))
def any_function_name(n-intervals):
1 Like
5

Thank you - that’s the step I was missing. Works great.

1 Like