Error deploying app services on Azure with Python 3.9 and Flask to process Excel files

I have the following environment deployed from VS Code

enter image description here

It was deployed in App Services on Azure using Python 3.9 and Flask to create an application on a B1 plan (Total ACU: 100, 1.75 GB memory, 1 vCPU). The app.py script is as follows:

from flask import Flask, render_template, request, send_file
import os
from scripts.misfunciones import process_data

app = Flask(__name__)

app.config['UPLOAD_FOLDER'] = os.path.join(os.path.dirname(__file__), 'uploads')

@app.route('/', methods=['GET', 'POST'])
def index():
    if request.method == 'POST':
        # Guardar los archivos subidos
        data_file = request.files['data_file']
        parametro_file = request.files['parametro_file']
        unidades_file = request.files['unidades_file']
        
        if not os.path.exists(app.config['UPLOAD_FOLDER']):
            os.makedirs(app.config['UPLOAD_FOLDER'])

        data_path = os.path.join(os.path.dirname(__file__), 'uploads', 'DATA.xlsx')
        parametro_path = os.path.join(os.path.dirname(__file__), 'uploads', '240424RF_Parametro.xlsx')
        unidades_path = os.path.join(os.path.dirname(__file__), 'uploads', '240306RF_Unidades.xlsx')
        output_path = os.path.join(os.path.dirname(__file__), 'uploads', 'DATA_FIN.xlsx')

        data_file.save(data_path)
        parametro_file.save(parametro_path)
        unidades_file.save(unidades_path)
        
        process_data(data_path, parametro_path, unidades_path, output_path)
        
        return send_file(output_path, as_attachment=True)

    return render_template('index.html')

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

and the script misfunciones.py:

import pandas as pd
import openpyxl
import re
chars_dict = {
    'n':'','*':'','°':'','(':'',')':'','+':'',
    '/':'','.':'','_':'',' ':'',',':'',''':'',
    'á':'a','é':'e','í':'i','ó':'o','ú':'u','-':''
}

def var_lower(df):
    for i in df.columns[1:]:
        df[str(i)] = df[str(i)].str.lower()
        
def remove_pattern(df, pattern):
    for column in df.columns:
        df[column] = df[column].replace(pattern, '', regex=True)
    return df

def process_data(data_path, parametro_path, unidades_path, output_path):
    DATA = pd.read_excel(data_path, engine='openpyxl')
    Parametro = pd.read_excel(parametro_path, engine='openpyxl')
    Unidades = pd.read_excel(unidades_path, engine='openpyxl')

    DATA_CORR = DATA.copy()
    Parametro_CORR = Parametro.copy()
    Unidades_CORR = Unidades.copy()

    DATA_CORR = remove_pattern(DATA_CORR, 'αφ')
    DATA_CORR = remove_pattern(DATA_CORR, 'αδ')
    DATA_CORR = remove_pattern(DATA_CORR, 'φ')

    var_lower(DATA_CORR)
    var_lower(Parametro_CORR)
    var_lower(Unidades_CORR)
    for char, replacement in chars_dict.items():
        escaped_char = re.escape(char)
        DATA_CORR = DATA_CORR.replace(escaped_char, replacement, regex=True)
        Parametro_CORR = Parametro_CORR.replace(escaped_char, replacement, regex=True)
        Unidades_CORR = Unidades_CORR.replace(escaped_char, replacement, regex=True)

    Unificar_Unidad = []
    cantidad = 0
    for i in DATA_CORR['ID-UNIDADES']:
        cantidad += 1
        for j in range(len(Unidades_CORR)):
            for k in Unidades_CORR.columns[1:]:
                if i == Unidades_CORR[k][j]:
                    Unificar_Unidad.append(j + 1)
                    break
            if cantidad == len(Unificar_Unidad):
                break
        if cantidad != len(Unificar_Unidad):
            Unificar_Unidad.append(9999)
    DATA['num_unid'] = Unificar_Unidad

    Unificar_Param = []
    cantidad = 0
    for i in DATA_CORR['ID-PARANETROS']:
        cantidad += 1
        for j in range(len(Parametro_CORR)):
            for k in Parametro_CORR.columns[1:]:
                if i == Parametro_CORR[k][j]:
                    Unificar_Param.append(j + 1)
                    break
            if cantidad == len(Unificar_Param):
                break
        if cantidad != len(Unificar_Param):
            Unificar_Param.append(9999)
    DATA['num_param'] = Unificar_Param

    DATA.to_excel(output_path, index=False)
    return output_path

script index.html:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Subir Archivos</title>
</head>
<body>
    <h1>Subir Archivos para Procesar</h1>
    <form method="POST" enctype="multipart/form-data">
        <label for="data_file">Archivo DATA:</label>
        <input type="file" name="data_file" id="data_file" required><br><br>
        <label for="parametro_file">Archivo Parametro:</label>
        <input type="file" name="parametro_file" id="parametro_file" required><br><br>
        <label for="unidades_file">Archivo Unidades:</label>
        <input type="file" name="unidades_file" id="unidades_file" required><br><br>
        <input type="submit" value="Procesar">
    </form>
</body>
</html>

However, the application gives an error
enter image description here

I have run it locally and it works correctly. I don’t know what is causing the problem, but I think it might be related to the Excel files or some kind of permission. An HTTP 503 error appears in the error list.

I have also tried running it in memory without storing the Excel files, and it worked locally, but not on Azure.

Please, I will appreciate your support to deploy this application correctly on azure.