Using Python Dataclass in Django Models

Question

My goal is to create a struct-like object in Django PostgreSQL, such as:

specs.coordinate.x
specs.coordinate.y
specs.coordinate.z

x,y,z should therefore be subclasses of coordinate. They should be me mutable as well, wherefore named tuples cannot be used.

I have tried it using the new dataclass:

from django.db import models
from dataclasses import dataclass

class Specs(models.Model):
    name = models.CharField(max_length=80)
    age = models.IntegerField()

    @dataclass
    class coordinate:
        x: float
        y: float
        z: float

However the coordinate x,y,z items are not visible in pgAdmin:

What am I doing wrong? Is there any better approach for this than with dataclass?

Answer 1

If your goal is simply to use the syntax: specs.coordinate.x in your datasheet you can simply use a OneToOne Relation.

This also allows for the special case, that either all Coordinates values have to be set or none.

from django.db import models

class Coordinate(models.Model):
    x = models.FloatField()
    y = models.FloatField()
    z = models.FloatField()


class Specs(models.Model):
    name = models.CharField(max_length=80)
    age = models.IntegerField()
    coordinate = models.OneToOneField(
        Coordinate, 
        null=True, 
        on_delete=models.SET_NULL
    )

Now you can use Specs just like the a Dataclass.