Reading JSON from Arduino over serial in python and writing to a JSON file on computer

I'm fairly new to Arduino so I used a sample code before integrating this into my main code. I'm printing my value in a JSON format over serial. My Arduino outputs this and the python receives this and prints it in the same format

{

"value" : 5

}

but when I use python to try writing to a JSON file on my computer, I'm not getting the same JSON format. Can anyone figure out what's wrong? I need to write to my JSON file in JSON format, but instead, I'm getting this format written in my JSON file " \"value\": 5\r\n" instead of {"value: 5"}. Another problem I'm getting is that sometimes the values I get in my JSON get cut off so sometimes I end up with \r\n" or other parts of the current output. My goal is to get the python code to overwrite the JSON file in real-time, so whenever I open the JSON file, the entire output should be there in the correct JSON format. Any help is appreciated, thank you.

Arduino Code:

#include <ArduinoJson.h>

int analogPin = 3;     
int data = 0; 
char userInput;          

StaticJsonDocument<100> testDocument;
char buffer[100];

void setup(){

  Serial.begin(9600);          //  setup serial

  StaticJsonDocument<100> testDocument;

  testDocument["sensorType"] = "Temperature";
  testDocument["value"] = 10;

  char buffer[100];

  serializeJsonPretty(testDocument, buffer);

  Serial.println(buffer);

}
int(i)=1;
void loop(){

    testDocument["value"] = i;

    serializeJsonPretty(testDocument, buffer);

    Serial.println(buffer);

    i=i+1;
 }

Python Code:

import serial
import json
import time

ser = serial.Serial('COM4', baudrate = 9600, timeout=1)

while 1:

    data = (ser.readline().decode('ascii')) #split('\r\n')

    #j = json.loads(data)


    file = "C:/Users/Mike/Desktop/test.json"

    my_data_file = open(file, 'w')

    with open(file1, "w") as my_data_file :
        json.dump(data, my_data_file)

    print(data)