Serializing Polymophic Hierarchy

I have decision tree where the nodes are subclasses to support different types of decisions. Not surprisingly, if I dump using the base Node schema I only get the fields in that class which doesn’t even include the sub-nodes. Like I said, no real surprise there.

Is the idea of serializing a set of classes that use polymorphism totally out of scope or something we could work towards in a future release?

I’ll poke away at some solutions. Maybe we can find something to incorporate into dcj.

import copy
import json
from abc import ABC, abstractmethod
from dataclasses import dataclass
from typing import MutableMapping

from dataclasses_json import dataclass_json


@dataclass_json
@dataclass
class Node(ABC):
    name: str

    @abstractmethod
    def decide(self, state: MutableMapping) -> bool:
        pass


@dataclass_json
@dataclass
class DecisionNode(Node):
    true_node: Node
    false_node: Node

    def __init__(self, name: str, true_node: Node, false_node: Node, var_key: str, value: int):
        self.true_node = true_node
        self.false_node = false_node
        self.var_key = var_key
        self.value = value
        super().__init__(name=name)

    def decide(self, state: MutableMapping) -> bool:
        state = copy.deepcopy(state)
        if state[self.var_key] > self.value:
            return self.true_node.decide(state)
        else:
            return self.false_node.decide(state)


@dataclass_json
@dataclass
class LeafNode(Node):
    result: bool

    def __init__(self, name: str, result: bool):
        self.result = result
        super().__init__(name=name)

    def decide(self, state) -> bool:
        return self.result


def decide():
    true_leaf = LeafNode(name="true", result=True)
    false_leaf = LeafNode(name="false", result=False)
    decision_node = DecisionNode(
        name="int value", true_node=true_leaf, false_node=false_leaf, var_key="year", value=2000
    )
    state = {"year": 2019}
    result = decision_node.decide(state)
    assert result

    print(json.dumps(Node.schema().dump(decision_node), indent=2))

if __name__ == "__main__":
    decide()

[NoamNol]

Any update? Is it possible without a Union?

[nathan5280]

@aronszanto My team has switched to FastAPI which uses Pydantic for the validation and mapping functionality that I so love in the lightweight DCJ package. It is unlikely that I’ll get back to this anytime soon. Feel free to ping me if you decide to move forward with this or want to bounce some ideas off me.