Example classes that can un-nest python POPOs

gqlflat.py

from __future__ import annotations
from collections import UserDict
from dataclasses import dataclass
from typing import Type, Any, Optional

import json

"""
Example how to simplify a heavily-nested POPO
using a set of declarative classes. This is motivated
by GraphQL responses which contain heavily-nested
objects

Each class defines a list of FieldSpec

FieldSpec
  - path attribute specifies the location of the value using
    dot notation for nested keys
  - dest attribute provides an alternate key, otherwise the 
    path leaf is used
  - klass attribute (optional) specifies another class to
    further process an inner object

"""

@dataclass
class FieldSpec:
    path: str
    dest: Optional[str] = None
    klass: Optional[Type[BaseGQLFlat]] = None


class BaseGQLFlat:
    _bare = False
    _dspec = []

    def __new__(self, src):
        data = None if self._bare else {}
        for cspec in self._dspec:
            _src = src
            for seg in cspec.path.split("."):
                if seg not in _src:
                    break
                _src = _src[seg]
            else:
                if isinstance(_src, list) and cspec.klass:
                    val = [
                        cspec.klass(item) for item in _src
                        if cspec.klass(item)
                    ]
                else:
                    val = cspec.klass(_src) if cspec.klass else _src

                if not self._bare:
                    if val is not None:
                        key = cspec.dest if cspec.dest else seg
                        data[key] = val
                else:
                    data = val
        return data


class Micro(BaseGQLFlat):
    _bare = True
    _dspec = [FieldSpec(path="b")]


class Nano(BaseGQLFlat):
    _dspec = [
        FieldSpec(path="fix.me", dest="apple"),
        FieldSpec(path="atl", klass=Micro),
    ]


class Newbie(BaseGQLFlat):
    _dspec = [
        FieldSpec(path="inner.tube"),
        FieldSpec(path="air.press.com", dest="apc"),
        FieldSpec(path="inner.casp", dest="hun", klass=Nano),
        FieldSpec(path="air.nothing.b"),
        FieldSpec(path="air.aruba", klass=Nano),
    ]



if __name__ == "__main__":

    gqlinput = {
    	"inner": {
    		"tube": 1234,
    		"ast": "abc",
    		"flex": ["a", "c", "e"],
            "casp": {
                "fix": {
                    "me": "is_hun",
                    "ignored": 231
                },
                "orange": "apple",
                "atl": [
                    {"a": 1, "b": 1},
                    {"a": 1, "c": 2},
                    {"a": 1, "b": 3},
                ]
            }
    	},
    	"air": {
            "press": {
                "com": {"a": "zzz", "b": "zyx"},
                "bbbb": 322,
            },
            "nothing": {"z": 1, "u": 55, "b": 66},
            "aruba": {
                "fix": {
                    "x": "xxxx"
                },
                "atl": {"k": "jjj"}
            },
        }
    }

    goutput = Newbie(gqlinput)

    print(goutput)
    print(f"{json.dumps(goutput, indent=2)}")