duplicate_keys.json

{
    "key":1234,
    "key":5678,
    "key":"abcd",
    "bork":"asdf",
    "bork":"dfsd"
}

duplicate_keys_json.py

"""Example Output:
$ python detect_duplicate_keys.py
Traceback (most recent call last):
  File "detect_duplicate_keys.py", line 43, in <module>
    print(detect_duplicates(json_file))
  File "detect_duplicate_keys.py", line 36, in detect_duplicates
    duplicate_keys, json_file
__main__.DuplicateKeysError: Duplicate keys(s): ['key', 'bork'] in json file: duplicate_keys.json
"""

import collections
import json
import pathlib


class DuplicateKeysError(Exception):
    pass


def detect_duplicates(json_file):
    """Raise exception if json_file contains multiple identical keys."""
    with json_file.open('r') as f:
        d = json.load(f, object_pairs_hook=list)

    keys = [key_value_pair[0] for key_value_pair in d]

    duplicate_keys = [
        key for key,count
        in collections.Counter(keys).items()
        if count > 1
    ]

    if len(duplicate_keys) != 0:
        raise DuplicateKeysError(
            "Duplicate key(s): {} in json file: {}".format(
                duplicate_keys, json_file
            )
        )


if __name__ == '__main__':
    json_file = pathlib.Path('.', 'duplicate_keys.json')
    detect_duplicates(json_file)