Is there a way to clear a dropdown from a callback?

Dash Python
1

I have quite a few dropdowns, some with set values from the beginning while others just have placeholder values (i.e. ‘Select X’). I have another button that resets all of the dropdowns but the value within the dropdown remains the same. For example, if I have a dropdown that is selecting fruits and the user selects apples to filter the data, and then they reset the filters (which clears all filters and would change the selected_fruit = None) the ‘apple’ would still remain in the dropdown box instead of the original placeholder.

TL;DR I want to have my callback clear my dropdown or reset it to the placeholder.

2

I think return value=[] in call back would work. Something as below:

from dash import Dash, dcc, html, Input, Output
from plotly.express import data
import pandas as pd

df =  data.medals_long()

app = Dash(__name__, external_stylesheets=[dbc.themes.LUX])
app.layout = dbc.Container([
    dbc.Row([
        dbc.Col([
            dcc.Dropdown(df.nation.unique(), 
                         id='pandas-dropdown-2',
                         clearable=True,placeholder='Please select'),
        ],width={'size':10}),
        dbc.Col([
            dbc.Button("Clear",id='btn'),
        ],width={'size':2}),
    ])
])

@app.callback(
    Output('pandas-dropdown-2', 'value'),
    Input('btn', 'n_clicks')
)
def update_value(n_clicks):
    if n_clicks > 1:
        return []


if __name__ == '__main__':
    app.run_server(debug=False)
1 Like
4

Maybe an MRE would help in this case.