flask框架研究：
https://blog.csdn.net/shifengboy/article/details/114274271
https://blog.csdn.net/weixin_67531112/article/details/128256170

实现下载文件功能

vim test.py
import io
from flask import Flask, send_file

app = Flask(__name__)
@app.route('/download', methods=['GET'])
def download_file():
    # 当前目录下创建文件对象
    filename = "file.txt"
    file = open(filename, "w")

    # 写入数据到文件
    file.write("Hello, World!")

    # 关闭文件
    file.close()

    try:
        # 尝试打开文件并发送
        return send_file(filename, as_attachment=True)
    except PermissionError:
        return {"code": 403, "message":"文件权限错误，无法访问", "data":""}
    except Exception as e:
        return {"code": 500, "message":"发生错误", "data": str(e)}

if __name__ == '__main__':
    #app.run()
    svhost="0.0.0.0"
    svport=9001
    app.run(debug=True, host=svhost, port=svport)

1.filename 变量中提供要下载的文件的路径。
2.当访问 download 路由时，会触发download_file 函数，该函数使用send_file 方法将文件发送到客户端以进行下载
3.as_attachment=True 表示将文件作为附件下载，而不是在浏览器中直接打开。

(base) user@ubuntu:~$ python test.py
 * Serving Flask app 'flash_send'
 * Debug mode: on
WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
 * Running on all addresses (0.0.0.0)
 * Running on http://127.0.0.1:9001
 * Running on http://192.168.98.169:9001
Press CTRL+C to quit
 * Restarting with watchdog (inotify)
 * Debugger is active!
 * Debugger PIN: 188-315-851

浏览器中输入 http://192.168.98.169:9001/download