服务器程序可以下载文件 " 图像 .jpg" import flask import os app=flask.Flask(__name__) @app.route("/") def index(): if "fileName" not in flask.request.values: return " 图像 .jpg" else: data = b"" try: _____________________________________________ if fileName != "" and os.path.exists(fileName): fobj = open(fileName, "rb") _________________________ fobj.close() except Exception as err: data = str(err).encode() return data if __name__=="__main__": app.run() 缺失的语句是