Get value from asymmetrically nested dict with unique keys

December 15, 2022

Say I have a nested dict, with asymmetrical nesting, and no key appearing more than once across the entire nested dict:

d = {
d1 : {d11: 'a', d12: 'b'}
d2 : {d21: 'c', d22: {d221: 'd', d222: 'e'}}
}

I would like a function (without a module) that returns the value of any of the (unique) keys, i.e.:

def get_some_val(d, key):
    ...
    return val_of_that_key

Anyone who could help me in the right direction? Thanks!

I tried passing the (nested) keys as strings, and then using exec to get the value, but this did not work

>Solution :

One approach:

d = {
    "d1": {"d11": 'a', "d12": 'b'},
    "d2": {"d21": 'c', "d22": {"d221": 'd', "d222": 'e'}}
}


def nested_find(needle, haystack):
    if needle in haystack:
        return haystack[needle]
    for v in haystack.values():
        if isinstance(v, dict):
            val = nested_find(needle, v)
            if val:
                return val


res = nested_find("d222", d)
print(res)

Output

A one-liner alternative is to do:

def nested_find(needle, haystack):
    gen = (val for v in haystack.values() if isinstance(v, dict) and (val := nested_find(needle, v)))
    return haystack.get(needle, next(gen, None))