Extract json subelements via command line and printout results on stdout.

json_extractor.py

#!/usr/bin/env python3
"""
Extract json subelements via command line and printout results on stdout.

Example call:

echo "{\"a\":100, \"b\": [1,2,3]}" | ./json_extractor.py b

will print:
[
    1,
    2,
    3
]
"""
import json
import sys


def is_int(x):
    """ check if x is an integer """
    try:
        xi = int(x)
        return True
    except Exception:
        return False


obj = ""
for l in sys.stdin:
    obj += l

try:
    j = json.loads(obj)
    for i in sys.argv[1:]:
        if is_int(i):
            # for array access convert parameter to int
            j = j[int(i)]
        else:
            j = j[i]
    print(json.dumps(j, indent=4, sort_keys=True))
except Exception as e:
    print('error: ' + str(e), file=sys.stderr)