find_key_in_arbitrary_structure.py

test = {
    'lol': ['wat', 'the', 'fuck'],
    'ten': 'pence',
    'who': {'did': 1, 'the': 2, 'poop': 3},
    'this': [{'goes': {'pretty': 'deep'}, 'if': {'I': 'may say so'}}]
}


class StopSearch(Exception):
    pass


def traverse(obj, key):
    if isinstance(obj, dict):
        if key in obj:
            raise StopSearch(key)
        return {k: traverse(v, key) for k, v in obj.items()}
    elif isinstance(obj, list):
        return [traverse(elem, key) for elem in obj]
    else:
        return obj


def find_traverse(target, key):
    try:
        traverse(target, key)
    except StopSearch:
        return True
    return False


find_traverse(test, 'pretty')