问Jupyter:使用dash应用程序重新运行我的cell会给我一个错误

EN

OSError: [Errno 98] Address already in use

import dash

import plotly.express as px
from jupyter_dash import JupyterDash
import dash_core_components as dcc
import dash_html_components as HTML
from dash.dependencies import Input, Output



app = dash.Dash("SimpleExample")
app.layout = html.Div([dcc.RadioItems(id='dropdown-color',
    options=[{'label': c, 'value': c.lower()}
             for c in ['Red', 'Green', 'Blue']],value='red'),
    html.Div(id='output-color'),dcc.RadioItems(id='dropdown-size',
    options=[{'label': i, 'value': j}
             for i, j in [('L','large'), ('M','medium'), ('S','small')]],
    value='medium'),
html.Div(id='output-size')])

@app.callback(
dash.dependencies.Output('output-color', 'children'),
[dash.dependencies.Input('dropdown-color', 'value')])
def callback_color(dropdown_value):
 return "The selected color is %s." % dropdown_value

@app.callback(
 dash.dependencies.Output('output-size', 'children'),
 [dash.dependencies.Input('dropdown-color', 'value'),
 dash.dependencies.Input('dropdown-size', 'value')])
def callback_size(dropdown_color, dropdown_size):
 return "The chosen T-shirt is a %s %s one." %(dropdown_size,
                                              dropdown_color)


if __name__ == '__main__':
 app.run_server(port = 8021, debug = True)