print_keys.py

import json
import sys


def p(key, indent):
    print('%s%s' % (' ' * (indent*2), key))


def print_object(obj, indent=0):

    if isinstance(obj, dict):
        items = sorted(list(obj.items()), key=lambda x: x[0])

        for k, v in items:
            p('- %s' % k, indent)
            print_object(v, indent+1)

    elif isinstance(obj, list):

        if len(obj) > 0:
            p('[', indent)
            print_object(obj[0], indent+1)
            p(']', indent)
        else:
            p('[]', indent)

if __name__ == '__main__':

    for f in sys.argv[1:]:
        with open(f) as fp:
            obj = json.loads(fp.read())
            print_object(obj)