“尝试在浏览器窗口中加载我的flask应用程序时出现URL未找到错误”

Question

下面是我的代码。我想通过我的flask应用程序将excel文件转换为json。运行代码后，尝试在浏览器中加载Flask URL时，localhost出现以下错误：

404 not found error - The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again

我需要做什么？下面是我的应用程序代码：

from flask import Flask, request, jsonify
import flask_excel as excel


app=Flask(__name__)

@app.route("/upload", methods=['GET', 'POST'])
def upload_file():
    if request.method == 'POST':
        return jsonify({"result": request.get_array(field_name='file')})
    return '''
    <!doctype html>
    <title>Upload an excel file</title>
    <form action="" method=post enctype=multipart/form-data>
    <p><input type=file name=file><input type=submit value=Upload>
   </form>
    '''

@app.route("/export", methods=['GET'])
def export_records():
    return excel.make_response_from_array([[1,2], [3, 4]], "csv",
                                          file_name="export_data")

if __name__ == "__main__":
    app.run()