How can I access nested JSON keys dynamically by using an array in Python?

Question

What I'd like to do, is to create a function, to which I pass a string array and a json, that would check if the json has the keys specified by the array and return their corresponding value. Here I have a snippet that works for top-level keys (and their values):

import json


def check_key_and_return(json, keys):
    if keys[0] in json:
        return json[keys[0]]
    else:
        return ''


if __name__ == '__main__':
    json_s = '{"a":{"b":1}}'
    json = json.loads(json_s)
    print(check_key_and_return(json, ['a']))

this returns {'b': 1} .

I'd like to be able to pass multiple strings, like check_key_and_return(json, ['a', 'b']) , so that the function would return 1 (or an empty string if no match is found.

Thank you.

Answer 1

Since nested keys become value for the parent key, you would have an iterator to fetch all keys. One of the ways could be:

import numpy as np
import pandas as pd
import json
from collections.abc import Mapping
def nested_keys(d) -> set:
    """
    Return a set containing all nested keys.
    """
    # If it is not a dict-like object, return an empty set
    if not isinstance(d, Mapping):
        return set()

    keys = d.keys()
    for v in d.values():
        # Update the keys set with the keys in each value by using the union (or) operator: |
        keys |= nested_keys(v)

    return keys

str='{"a":{"b":1}}'
json_str = json.loads(str)
print(json_str)
all_keys=nested_keys(json_str)
print(nested_keys(json_str))
find_set1={'a','c'}
print(find_set1.issubset(all_keys))
find_set2={'a','b'}
print(find_set2.issubset(all_keys))

Output:

{'a': {'b': 1}}
{'a', 'b'}
False
True

Now based on the above condition(True/False) you can return 1 or empty string.