CODEWITHSUNDEEP
pythonplotly-dash
jf328
jf328

Reputation: 7351

plotly dash, callback with 2 button inputs and a dropdown input

How can I write a callback such that if button 1 is clicked, do A; if button 2 is clicked, do B; if a dropdown value is changed, do C?

import dash
import dash_core_components as dcc
import dash_html_components as html

app = dash.Dash(__name__)
app.layout = html.Div([
        html.H1('initial', id = 'h1'),
        html.Button('to upper', id = 'upper button', n_clicks_timestamp = '0'),
        html.Button('to lower', id = 'lower button', n_clicks_timestamp = '0'),
        dcc.Dropdown(options = [{'value':s, 'label': s} for s in ['good','bad']], value = 'good', id = 'set string')
    ])

@app.callback(
         dash.dependencies.Output('h1', 'children'),
         [dash.dependencies.Input('upper button', 'n_clicks_timestamp'), 
          dash.dependencies.Input('lower button', 'n_clicks_timestamp'), 
          dash.dependencies.Input('set string', 'value')],
         [dash.dependencies.State('h1', 'children')]
    )
def update(upper, lower, newstring, currentstring):
    upper, lower = int(upper), int(lower)

    # ???
    # if dropdown changed, return newstring
    # ???

    if upper > lower:
        return currentstring.upper()
    if lower > upper:
        return currentstring.lower()

    return newstring

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

Since the dropdown doesn't have a timestamp property, there is no way to decide if it is the latest change.

Upvotes: 1

Views: 4525

Answers (1)

giobatta912
giobatta912

Reputation: 190

Do the buttons get to be pressed multiple times in your callback? If not, when the callback is triggered by the dropdown, the buttons will have 0 as n_clicks and None (or also 0, I don't recall) as n_clicks_timestamp. So you can infer that the dropdown triggered the callback, by process of elimination.

If the buttons get to be pressed multiple times, you need to create another callback on the children property of a Div containing the buttons, and simply re-instantiate the buttons, so that they will still be at 0 n_clicks and timestamp for the next callback.

Upvotes: 1

Related Questions