keygetter

>>> keygetter({ "food": { "breakfast": "cereal" } }, "food")
{'breakfast': 'cereal'}

>>> keygetter({ "food": { "breakfast": "cereal" } }, "food__breakfast")
'cereal'

>>> from typing import List, Optional
>>> from dataclasses import dataclass, field

>>> @dataclass()
... class Food:
...     fruit: List[str] = field(default_factory=list)
...     breakfast: Optional[str] = None

>>> @dataclass()
... class Restaurant:
...     place: str
...     city: str
...     state: str
...     food: Food = field(default_factory=Food)

>>> restaurant = Restaurant(
...     place="Largo",
...     city="Tampa",
...     state="Florida",
...     food=Food(
...         fruit=["banana", "orange"], breakfast="cereal"
...     )
... )

>>> restaurant
Restaurant(place='Largo',
    city='Tampa',
    state='Florida',
    food=Food(fruit=['banana', 'orange'], breakfast='cereal'))

>>> keygetter(restaurant, "food")
Food(fruit=['banana', 'orange'], breakfast='cereal')

>>> keygetter(restaurant, "food__breakfast")
'cereal'