Welcome @mikej! The example that you found in the user guide is the right example to be looking at. In fact, you should be able to just change that example from dcc.RadioItems
to dcc.Dropdown
and it should work:
# -*- coding: utf-8 -*-
import dash
from dash.dependencies import Input, Output
import dash_core_components as dcc
import dash_html_components as html
app = dash.Dash(__name__)
all_options = {
'America': ['New York City', 'San Francisco', 'Cincinnati'],
'Canada': [u'Montréal', 'Toronto', 'Ottawa']
}
app.layout = html.Div([
dcc.Dropdown(
id='countries-dropdown',
options=[{'label': k, 'value': k} for k in all_options.keys()],
value='America'
),
html.Hr(),
dcc.Dropdown(id='cities-dropdown'),
html.Hr(),
html.Div(id='display-selected-values')
])
@app.callback(
dash.dependencies.Output('cities-dropdown', 'options'),
[dash.dependencies.Input('countries-dropdown', 'value')])
def set_cities_options(selected_country):
return [{'label': i, 'value': i} for i in all_options[selected_country]]
@app.callback(
dash.dependencies.Output('cities-dropdown', 'value'),
[dash.dependencies.Input('cities-dropdown', 'options')])
def set_cities_value(available_options):
return available_options[0]['value']
@app.callback(
dash.dependencies.Output('display-selected-values', 'children'),
[dash.dependencies.Input('countries-dropdown', 'value'),
dash.dependencies.Input('cities-dropdown', 'value')])
def set_display_children(selected_country, selected_city):
return u'{} is a city in {}'.format(
selected_city, selected_country,
)
if __name__ == '__main__':
app.run_server(debug=True)