I have been working with similar functionality and after a bit of messing around with the ajax and python, this is what I came up with for python reading the ajax data

JavaScript:

var data ={
      data: JSON.stringify({"value":'asdf'})}};

$.ajax({
   url:"/",
   type:'POST',
   data: data,
   success
 
: function(msg){
              alert(msg);}})

Python:

from flask import json
@app.route("/", methods=['POST'])def get_data():
    data = json.loads(request.form.get('data'))
    ss = data['value']return str(ss)

注意：

javascript 不能如下寫法，不知為什麼：

$.ajax({
   url:"/",
   type:'POST',
   data: {"value":"val1"}
 
,
   success: function(msg){
              alert(msg);}})