ajax:
function ajaxFunction(point,route_code){
    console.log(route_code)
    $.ajax({
        type : 'POST',
        method: 'POST',
        url : "/new_coords",
        contentType: 'application/json',
        headers: {'Accept':'application/json'},
        data : {code: route_code},
        success: function(data){
            //new_coordinates(point,)
            console.log(data)
        }
      });
}

Flask router:
@app.route("/new_coords",methods=['POST'])
def new_coords():
    print(request.data) //менял на request.json, ошибка 400
	//выводит b'code=1232456'
    return 1