flattendict.py

from typing import Any, Dict


def flatten(data: Any, parent_key: str = "") -> Any:
    if isinstance(data, list):
        data = {str(i): x for i, x in enumerate(data)}

    if not isinstance(data, dict):
        return data

    ret: Dict[str, Any] = {}
    for key, value in data.items():
        value = flatten(value, key)
        if isinstance(value, dict):
            ret.update(value)
        else:
            ret[key] = value

    if not parent_key:
        return ret

    return {f"{parent_key}.{k}": v for k, v in ret.items()}


def unflatten(data: Any) -> Any:
    if not isinstance(data, dict):
        return data

    if all(key.isdigit() for key in data):
        return [unflatten(value) for _, value in sorted(data.items())]

    ret: Dict[str, Any] = {}
    for key, value in sorted(data.items()):
        value = unflatten(value)
        if "." in key:
            topkey, subkey = key.split(".", 1)
            ret[topkey] = ret.get(topkey, {})
            ret[topkey][subkey] = value
        else:
            ret[key] = value

    for key, value in ret.items():
        if isinstance(value, dict):
            ret[key] = unflatten(value)

    return ret


if __name__ == "__main__":
    data = {"a": {"b": 1, "c": 2}, "d": {"e": {"f": [3, 4, 5]}}}
    x = flatten(data)
    y = unflatten(x)
    print(x)
    print(y)