Plotly Dash:使用下拉输入更新图形

import dash
from dash import dcc, html
from dash.dependencies import Input, Output
import plotly.graph_objs as go

app = dash.Dash(__name__)

app.layout = html.Div([
    dcc.Dropdown(
        id='dropdown',
        options=[
            {'label': 'Line Chart', 'value': 'line'},
            {'label': 'Bar Chart', 'value': 'bar'}
        ],
        value='line'
    ),
    dcc.Graph(id='graph')
])

@app.callback(
    Output('graph', 'figure'),
    [Input('dropdown', 'value')]
)
def update_graph(selected_chart):
    if selected_chart == 'line':
        return go.Figure(data=[go.Scatter(x=[1, 2, 3], y=[4, 1, 2])])
    elif selected_chart == 'bar':
        return go.Figure(data=[go.Bar(x=[1, 2, 3], y=[4, 1, 2])])

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