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How could be realize a button can click it to generate the file and then click again to download this file

Here is my main code

import os
from urllib.parse import quote as urlquote
from flask import Flask, send_from_directory,send_file
import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output, State
from script.modeling_output_to_excel.modeling_output_to_excel import result_to_excel
from script.modeling_output_to_excel.generate import model, generate_plot, model_plot

UPLOAD_DIRECTORY = "data/interim/test"

if not os.path.exists(UPLOAD_DIRECTORY):

server = Flask(__name__, static_folder="assets")
app = dash.Dash(server=server)
app.config["suppress_callback_exceptions"] = True

def download(path):
    """Serve a file from the upload directory."""
    return send_from_directory(UPLOAD_DIRECTORY, path, as_attachment=True)

app.layout = html.Div(
        html.Button("Generate The Report", id="download_button", n_clicks=0),
        html.Div(id = "file_list")

    style={"display": "inline-block", "width": "30%", "margin": "auto"},

def uploaded_files():
    """List the files in the upload directory."""
    files = []
    for filename in os.listdir(UPLOAD_DIRECTORY):
        path = os.path.join(UPLOAD_DIRECTORY, filename)
        if os.path.isfile(path):
    return files

def file_download_link(filename):
    location = "/download/{}".format(urlquote(filename))
    return html.A(
        html.Button("Click To Download The Report"),
    [Output("file_list", "children"),
    [Input("download_button", "n_clicks")],
def update_output(n_clicks):
    path = UPLOAD_DIRECTORY + '/Report Demo.xlsx'
    if os.path.exists(path):
    if n_clicks > 0:
        generate_report(). ## This function use to generate file for download
        files = uploaded_files()

        return [(file_download_link(filename)) for filename in files], None

if __name__ == "__main__":
        debug=True, port=8099, dev_tools_ui=False, dev_tools_props_check=False

For now,this logic was clicking the button of generate the report get a file,then another button of download was shown up, click the download button, download this file.But,I wanna realize this scene is:click the button generate the report, then the text on the button changed from generate the report to download report,click again this button to execute download.Just one button,not two. Any help will appreciate it