How can I serialize a one to many relationship? about pydapper

[zschumacher]

Yes its possible! Good call out tho, I should add this to the docs.

import typing

import pydapper
from dataclasses import dataclass
import devtools

MY_DSN = "sqlite://pydapper.sqlite"


@dataclass
class Owner:
    id: int
    name: str
    tasks: typing.List["Task"]


@dataclass
class Task:
    id: int
    description: str


sql = """
select task.id as task_id,
       owner.id as owner_id,
       owner.name as owner_name,
       task.description as description
  from owner
  join task on owner.id = task.owner_id 
"""


with pydapper.connect(MY_DSN) as commands:
    results = commands.query(sql, buffered=False)  # lazy load results

    owners = dict()
    for record in results:
        owner_id = record["owner_id"]
        if owner_id not in owners:
            owners[owner_id] = Owner(id=owner_id, name=record["owner_name"], tasks=list())
        owners[owner_id].tasks.append(
            Task(id=record["task_id"], description=record["description"])
        )


devtools.debug(list(owners.values()))

[zschumacher]

that gives me this

[
        Owner(
            id=1,
            name='Zach Schumacher',
            tasks=[
                Task(
                    id=1,
                    description='Set up a test database',
                ),
                Task(
                    id=2,
                    description='Seed the test database',
                ),
                Task(
                    id=3,
                    description='Run the test suite',
                ),
            ],
        ),
    ]