Write gzipped Json objects into a Json file without loading it

I want to write dicts as gzipped json objects into a json file.

I had some solutions, but as the file got bigger the appending process got slower and slower.
So loading the file was not the way.

I found the solution here with:

def append_record_seek(data,filename):
    print('append_record_seek started with data:{data} filename:{filename}')
    with open (filename, mode="r+") as file:
        file.seek(os.stat(filename).st_size -1)
        file.write( ",]".format(json.dumps(data)) )

Later i want to read that file as a list of dicts.

Here is my minimal Code example:

import global_variables as gv
import time
import json as json
import base64
import io
import sys
import cv2
import gzip

import numpy as np

import os

from numpy import asarray
from json import JSONEncoder




data = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
path = r'C:/Videotool/Data'
name = 'test'
filename = path + '/' + name + '.json'
isExist = os.path.exists(path)
if not isExist:
    os.makedirs(path)
os.chdir(path)




def first_writer(data,filename):
    print(f'first_writer started with data:{data} filename:{filename}')
    with open (filename, 'w') as file:
        file.write('[')
        file.write(json.dumps(data))
        file.write(',')
        file.write(']')

        
def append_record_seek(data,filename):
    print('append_record_seek started with data:{data} filename:{filename}')
    with open (filename, mode="r+") as file:
        file.seek(os.stat(filename).st_size -1)
        file.write( ",]".format(json.dumps(data)) )




for x in range(6):
    print(f'step:{x}')
    file_exists = os.path.exists(name+'.json')
    if file_exists:
        print('file_exists')
        append_record_seek(data,filename)
    else:
        print('else')
        first_writer(data,filename)

the non zipped result should be looking like:

[{"brand": "Ford", "model": "Mustang", "year": 1964},
{"brand": "Ford", "model": "Mustang", "year": 1964},
{"brand": "Ford", "model": "Mustang", "year": 1964},
{"brand": "Ford", "model": "Mustang", "year": 1964},
{"brand": "Ford", "model": "Mustang", "year": 1964}]

My result is : [{"brand": "Ford", "model": "Mustang", "year": 1964},,,,,,]

If that works, i want to zip the dumps before writing.

I hope somebody can help

Update:
I've got the right Json format with:

def first_writer(data,filename):
    print(f'first_writer started with data:{data} filename:{filename}')
    with open (filename, 'w') as file:
        file.write( "[{}]".format(json.dumps(data)) )

        
def append_record_seek(data,filename):
    print('append_record_seek started with data:{data} filename:{filename}')
    with open (filename, mode="r+") as file:
        file.seek(os.stat(filename).st_size -1)
        file.write( ",{}]".format(json.dumps(data)) )

Now i have to get that zipped...

NOTE: This is not the answer to the question, as there is none, this will just highlight that a single compressed file can be generated and decompressed later but it will not be valid json.

import gzip
from copy import copy
import json

# just test data
x = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
z = {
  "brand": "Mato",
  "model": "Laatikko",
  "year": 2023
}

l = []

# populate the initial "json" in the list l
for i in range(3):
  y = copy(x)
  y["year"] += i
  l.append(y)

# write list of dicts as jsons string into file and compress it via gzip
# it doesnt really matter how this was originally done..
with open("data.gz", "wb") as f:
   f.write(gzip.compress(bytes(json.dumps(l, indent=2),"utf-8")))

# then, append a new entry to the same file -- which will get uncompressed
# with the previously stored *valid* json structure..

with open("data.gz", "ab") as f:
   f.write(gzip.compress(bytes(json.dumps(z, indent=2),"utf-8")))

This will result a file that looks like this when uncompressed

[
  {
    "brand": "Ford",
    "model": "Mustang",
    "year": 1964
  },
  {
    "brand": "Ford",
    "model": "Mustang",
    "year": 1965
  },
  {
    "brand": "Ford",
    "model": "Mustang",
    "year": 1966
  }
]{
  "brand": "Mato",
  "model": "Laatikko",
  "year": 2023
}