snippets/get-json-key.py

#!/usr/bin/env python3

import fileinput, sys, json, functools
from typing import Union, List

JsonKey = Union[str, int]

def try_int(x: str) -> JsonKey:
    try:
        return int(x)
    except:
        return x

def main(indices: List[str]) -> None:
    for line in fileinput.input(files=('-',)):
        data = json.loads(line)
        try:
            val = functools.reduce(lambda x, i: x[try_int(i)], indices, data)
        except Exception as e:
            print('indexing json data failed with keys {}: {}\n'.format(' > '.join(indices), e), file=sys.stderr)
            raise e
        print(val)

if __name__ == '__main__':
    if len(sys.argv) < 2:
        print('USAGE: ./get-json-key.py [KEY].. < json-input', file=sys.stderr)
        sys.exit(1)
    main(sys.argv[1:])