Name is not defined only in one chart

Dash Python
1

Hi,

  1. I parse uploaded data and return df_con:
    Result: OK
def parse_data(contents, filename):
    content_type, content_string = contents.split(',')
    global df_con
    decoded = base64.b64decode(content_string)
    try:
        if 'csv' in filename:
            # Assume that the user uploaded a CSV or TXT file
            df_con = pd.read_csv(
                io.StringIO(decoded.decode('utf-8')))
        elif 'xls' in filename:
            # Assume that the user uploaded an excel file
            df_con = pd.read_excel(io.BytesIO(decoded))
        elif 'txt' or 'tsv' in filename:
            # Assume that the user upl, delimiter = r'\s+'oaded an excel file
            df_con = pd.read_csv(
                io.StringIO(decoded.decode('utf-8')), delimiter = r'\s+')
    except Exception as e:
        print(e)
        return html.Div([
            'There was an error processing this file.'
        ])

    return df_con
  1. Then create callback and make a Scatter.
    Result: Chart is OK, but there is (minor) error “local variable ‘df_con’ referenced before assignment”.
@app.callback(Output('graph3', 'figure'),
              [Input('upload-data', 'contents'),
                Input('upload-data', 'filename')])
def update_graph_upload(contents, filename):
    if contents:
        contents = contents[0]
        filename = filename[0]
        df_con = parse_data(contents, filename)
    fig2 = go.Figure(
        data=[
            go.Scatter(
                x=df_con['datetime'], 
                y=df_con['fact'], 
                mode='lines+markers')
            ],
        layout=go.Layout(
            plot_bgcolor=colors["graphBackground"],
            paper_bgcolor=colors["graphBackground"]
        ))
    return fig2
  1. Create a function to analize uploaded data and return dfcnb
    Result: Seems OK. (working on others script)
def bal_costs_df(df_con):

    con = pyodbc.connect(
        'Driver={SQL Server};'
        'Server=HTIC--DB1.RF.RES;'
        'Database=EKX;'
        'Trusted_Connection=yes;'
    )

    df_con['plan'] = df_con['fact'].shift(168)
    querystringnp = f"""
        SELECT [ELSPOTP_LT_DATE_ID],
                  [ELSPOTP_LT_TIME_ID],
                  [ELSPOTP_PRICE]
        FROM [ET_DWH].[dbo].[FactElspotPrices]
        WHERE ELSPOTP_PAREA_ID = 1
        ORDER BY ELSPOTP_LT_DATE_ID
    """
    cursor = con.cursor()
    df_np = pd.read_sql(querystringnp, con) 
    
    #Many other data manipulation and return....
            
    return dfcnb
  1. Try to create another chart based on df_con and bal_costs_df function.
    Result: Got error name ‘df_con’ is not defined.
@app.callback(Output('graph4', 'figure'),
              [Input('upload-data', 'contents'),
                Input('upload-data', 'filename')])
def update_graph2(contents, filename):
    dfm = bal_costs_df(df_con)  <<<<<<<<<<<<ERROR: "name 'df_con' is not defined"
    fig3 = go.Figure(
        data=[
            go.Scatter(
                x=dfm['datetime'], 
                y=dfm['balcosts'], 
                mode='lines+markers')
            ],
        layout=go.Layout(
            plot_bgcolor=colors["graphBackground"],
            paper_bgcolor=colors["graphBackground"]
        ))
    return fig3

Any ideas why for graph3 is ok, but for graph4 df_con is not defined? Maybe inputs are wrong?
I want to have data as in dfcnb dataframe and create a chart from it.
Thanks