Flask request.get_json() not receiving anything from $.post() request

Question

I am trying to communicate data between JavaScript and Python, and I am doing that by using JSON variables, but it seems that whenever I make a POST request from JavaScript, request.get_json() in the Python receiver method is not picking up anything and prints None when I print request.get_json().

The Python method works where it will return something back to JS, but it is always None. Am I doing something wrong in my $.post() method?

JavaScript $.post() call:

var items = {"robotCoor": {"robot_x": 1, "robot_y": 1},
         "gridParams": {"goal_y": 0, "size_x": 16, "size_y": 16, "goal_x": 0},
         "obsParams": {"obs_x3": 0, "obs_x4": 0, "obs_y4": 0, "obs_x2": 0, "obs_x1": 0, "obs_y1": 0, "obs_y2": 0, "obs_y3": 0},
         "aiParams": {"layers": 0, "learning_rate": 0, "speed": 0}
     };
var stuff = JSON.stringify(items);
console.log(stuff); #prints the correct thing
$.post("receiver", stuff, function( data ) {
    console.log(stuff); #prints the correct thing
    alert("Data: " + data); #alerts with "Data: None"
});

Python receiver method:

@app.route("/receiver", methods = ["POST"])
def receiver():
    if request.method == "POST":
        stuff = request.get_json()
        print(stuff) #prints None
        stuff = str(stuff)
        print(stuff) #prints None

        return stuff

score 5 · Accepted Answer · answered Jun 24 '18 at 18:07

In your JavaScript, set the Content-Type for the request to application/json. Otherwise get_json will always return None. One way to do this is to do the following[1]

$.ajaxSetup({
  contentType: "application/json; charset=utf-8"
});

Alternatively, you can attempt to force Flask to ignore the content type by using get_json(force=True)[2]

Flask request.get_json() not receiving anything from $.post() request

1 Answers1