python-json-format created by antonalekseev - https://repl.it/@antonalekseev/python-json-format

file.json

{ "value": [1, 2, 3, 4, 5] }

file1.json

{
    "value": [
        2,
        3,
        4,
        5,
        6
    ]
}

main.py

import json

with open("file.json", "r", encoding="utf-8") as fd:
  content = json.load(fd)
  content["value"] = [int(x) + 1 for x in content["value"]]

with open("file1.json", "w", encoding="utf-8") as fd:
  json.dump(content, fd, indent=4)