deep flatten nested dict

deep_flatten.py

def deep_flatten(data: dict, flatten_result: dict = {}, parent_key: str = ""):
    for key, value in data.items():
        target_key = f"{parent_key}.{key}" if parent_key else key 
        if isinstance(value, dict):
            deep_flatten(value, flatten_result, target_key)
        else:
            flatten_result[target_key] = value
    return flatten_result

assert deep_flatten(
{
    "a": "1",
    "b": {
        "b1": "testing_b1",
        "b2": 123,
        "b3": {"b1_1": 1, "b1_2": 2, "b1_3": "test-inner-b1_3"},
    },
    "c": {"c1": [1, 2, 3], "c2": 0, "c3": None},
}) == {
    "a": "1",
    "b.b1": "testing_b1",
    "b.b2": 123,
    "b.b3.b1_1": 1,
    "b.b3.b1_2": 2,
    "b.b3.b1_3": "test-inner-b1_3",
    "c.c1": [1, 2, 3],
    "c.c2": 0,
    "c.c3": None,
}