Maintaining foreign key relations when casting to dict

Question

Say I have the following db classes:

class Person(DB.Entity):
  id = PrimaryKey(int, auto=True)
  name = Required(str, 100)
  cars = Set('Car')

class Car(DB.Entity):
  id = PrimaryKey(int, auto=True)
  owner = Required(Person, cascade_delete=False)

When I perform a select on Person, I get the associated cars:

people = Person.select(lambda p: p.name == 'Jaewon')

However, I would like to return people as a Dict instead of a Pony object, so it can be used in the calling methods. If I do the following, I get people as a dictionary, but lose the car key:

return people[:]

What is the proper way to pull values from the database and return them as dict without dropping their associated values?

Answer 1

The Entity.to_dict function has a related_objects keyword argument.

You can use it to include the objects in the dicts.

If you want the to-many relationships too, you also need the with_collections argument.

people = Person.select(lambda p: p.name == 'Jaewon')

people = [
  person.to_dict(
    related_objects=True,
    with_collections=True
  )
  for person in people
]

This doesn't automatically recurse, and you will have to walk the tree yourself to create the full dict.

for person in people:
  person['cars'] = [car.to_dict(**kwargs) for car in person['cars']]