Convert Python Class with Inner Classes and Static Attributes to JSON

Question

I am trying to convert the following to json.

@dataclass
class Attribute:
    name: str
    description: str


class A:
    class B:
        attr1 = Attribute(name="attr1",description="description")
        attr2 = Attribute(name="attr2",description="description")
    class C:
        attr3 = Attribute(name="attr3",description="description")
        attr4 = Attribute(name="attr4",description="description")

The expected output should be

{
    A:{
        B:{
            attr1:{
                name: "attr1",
                description: "description"
            },
            attr2:{
                name: "attr2",
                description: "description"
            }
        },
        C:{
            attr3:{
                name: "attr3",
                description: "description"
            },
            attr4:{
                name: "attr4",
                description: "description"
            }
        }
    }
}

What I have tried without success:

• using jsonpickle to encode the object (doesn't return the static class variables)

Answer 1

In this case, the simplest option I could suggest would be to define a recursive helper function to iterate over the static fields in a class and call dataclasses.asdict() on each, such as below.

Note: the following should work in Python 3.8+, as it uses the := walrus operator.

# noinspection PyProtectedMember, PyUnresolvedReferences
from dataclasses import asdict, _FIELDS


def to_dict(o, include_name=False):
    # check for dataclass instances
    if hasattr(o, _FIELDS):
        return asdict(o)

    # check we have a class
    if not isinstance(o, type):
        return None

    _dict = {k: res for k, v in o.__dict__.items() if (res := to_dict(v))}

    return {o.__qualname__: _dict} if include_name else _dict

Usage would then be as so:

import json
from dataclasses import dataclass


@dataclass
class Attribute:
    name: str
    description: str


class A:
    class B:
        attr1 = Attribute(name="attr1", description="description")
        attr2 = Attribute(name="attr2", description="description")

    class C:
        attr3 = Attribute(name="attr3", description="description")
        attr4 = Attribute(name="attr4", description="description")


print(json.dumps(to_dict(A, include_name=True), indent=2))

Prints:

{
  "A": {
    "B": {
      "attr1": {
        "name": "attr1",
        "description": "description"
      },
      "attr2": {
        "name": "attr2",
        "description": "description"
      }
    },
    "C": {
      "attr3": {
        "name": "attr3",
        "description": "description"
      },
      "attr4": {
        "name": "attr4",
        "description": "description"
      }
    }
  }
}