Python code to deep sort a JSON file

sort-json.py

import argparse
import collections
import json
import sys

def sort_json(json_obj):
    if isinstance(json_obj, dict):
        sorted_dict = collections.OrderedDict()
        for key in sorted(json_obj.keys()):
            sorted_dict[key] = sort_json(json_obj[key])
        return sorted_dict
    elif isinstance(json_obj, list):
        sorted_list = []
        for item in json_obj:
            sorted_list.append(sort_json(item))
        return sorted(sorted_list)
    else:
        return json_obj

if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('infile', nargs='?', type=argparse.FileType('r'), default=sys.stdin)
    parser.add_argument('outfile', nargs='?', type=argparse.FileType('w'), default=sys.stdout)
    parser.add_argument('--indent', default=4, type=int)

    args = parser.parse_args()

    if sys.stdin.isatty():
        parser.print_help()
        exit()

     # Load JSON data
    parsed_json = json.load(args.infile)

    # Sort JSON data
    sorted_json = sort_json(parsed_json)

    # Print sorted JSON
    print(json.dumps(sorted_json, indent=args.indent), file=args.outfile)