CALLBACKS_I tried to replicate an example to understand how callbacks work, got an error

Hi everyone! i’m new on dash and on this nice community. Here below my script that doesn’t work.

ERROR

dash.exceptions.InvalidCallbackReturnValue: The callback …piechart.figure… is a multi-output.
Expected the output type to be a list or tuple …:

CSV

The csv it’s like this one below (how can I upoad csv also? is it possible)

|RIDEID|REASONCODE|DEVICECLASSID|

|linea1|54|12|
|linea2|55|13|
|linea3|56|14|
|linea4|57|15|
|linea5|58|16|
|linea6|59|17|

–

SCRIPT

import dash_core_components as dcc
import dash
import dash_html_components as html
import dash_table
import pandas
import plotly
import plotly.express as px
from dash.dependencies import Input, Output

external_stylesheets = [‘https://codepen.io/chriddyp/pen/bWLwgP.css’]
app = dash.Dash(name, external_stylesheets=external_stylesheets)

csv = pandas.read_csv(‘C:\Users\acer\Desktop\Lorenzo\GTT\convalide\esportazione716_3.csv’, sep=’;’, low_memory = False)

app.layout = html.Div([
html.H1(children=‘Hello World’,
style = {
‘textAlign’ : ‘center’,
‘color’ : ‘#ff0000’
}
),

html.Div('prova'),

html.Div([
dash_table.DataTable(
id=‘table’,
columns=[{“name”: i, “id”: i, “deletable”: False, “selectable”: False} for i in csv.columns],
data=csv.to_dict(‘records’),
page_size=10,
editable=False,
filter_action=“native”,
sort_action=“native”,
sort_mode=“multi”,
row_selectable=“multi”,
row_deletable=False,
selected_rows=,
page_action=“native”,
page_current=0,
style_cell_conditional=[
{‘if’: {‘column_id’: ‘VALIDATIONSERIALNO’},
‘width’: ‘30%’, ‘textAlign’: ‘right’},
{‘if’: {‘column_id’: ‘ISSUINGDATE’},
‘width’: ‘30%’, ‘textAlign’: ‘left’},
{‘if’: {‘column_id’: ‘DATEANDTIME’},
‘width’: ‘30%’, ‘textAlign’: ‘left’},
],
),
], className=‘row’),

html.Div([
    html.Div([
        dcc.Dropdown(id='linedropdown',
            options=[
                     {'label': 'REASONCODE2', 'value': 'REASONCODE'},
                     {'label': 'DEVICECLASSID2', 'value': 'DEVICECLASSID'}
            ],
            value='DEVICECLASSID',
            multi=False,
            clearable=False
        ),
    ],className='six columns'),

    html.Div([
        dcc.Dropdown(id='piedropdown',
            options=[
                 {'label': 'REASONCODE1', 'value': 'REASONCODE'},
                 {'label': 'DEVICECLASSID1', 'value': 'DEVICECLASSID'}
            ],
            value='DEVICECLASSID',
            multi=False,
            clearable=False
        ),
    ],className='six columns'),

],className='row'),

html.Div([
    html.Div([
        dcc.Graph(id='linechart'),
    ],className='six columns'),

    html.Div([
        dcc.Graph(id='piechart'),
    ],className='six columns'),

],className='row'),

html.H2(children='Arrivederci'),

])

@app.callback(
[Output(‘piechart’, ‘figure’)],
#Output(‘linechart’, ‘figure’)],
[Input(‘table’, ‘selected_rows’),
Input(‘piedropdown’, ‘value’)]
#Input(‘linedropdown’, ‘value’)]
)
def update_data(chosen_rows,piedropval):
if len(chosen_rows)==0:
df_filterd = csv[csv[‘RIDEID’].isin([‘linea1’, ‘linea2’])]
else:
print(chosen_rows)
df_filterd = csv[csv.index.isin(chosen_rows)]

pie_chart=px.pie(
        data_frame=df_filterd,
        names='RIDEID',
        values=piedropval,
        hole=.3,
        labels={'RIDEID':'RIDEID1'}
        )



return (pie_chart)

if name == ‘main’:
app.run_server(debug=True)

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