#!/usr/bin/env python3
import json
import argparse

parser = argparse.ArgumentParser(
    description='sort json keys',
    formatter_class=argparse.ArgumentDefaultsHelpFormatter
)
parser.add_argument('filename', nargs=1)
parser.add_argument('-I', '--indent', type=int, dest='indent', default=None)

args = parser.parse_args()

with open(args.filename[0]) as f:
    data = json.load(f)
    print(json.dumps(
        data,
        indent=args.indent,
        sort_keys=True,
    ))