How to define a marshamllow List field using marshmallow_sqlalchemy

Question

I'm trying to create a Schema using marshmallow_sqlalchemy. I want to create a list out of two entries of the Database, x_coordinate and y_coordinate, however, I'm not sure how to do that.

Here's the Schema

from marshmallow_sqlalchemy import SQLAlchemySchema, auto_field
class LocationSQLAlchemySchema(SQLAlchemySchema):
    class Meta:
        model = Location
        load_instance = True
    
    location_id = auto_field('id')
    name = auto_field('name')
    user_uid = auto_field('customer_id')
    maps_url = auto_field('maps_url')
    coordinates = fields.List(Meta.model.x_coordinate,Meta.model.y_coordinate) #This is what I don't know how to define.

Here's the Model I'm using for this Schema:

from flask_sqlalchemy import SQLAlchemy
from sqlalchemy.dialects.mysql import INTEGER
db = SQLAlchemy()
class Location(db.Model):
    __tablename__ = 'cleaning_locations'
    id = db.Column(db.String(128), primary_key=True, unique = True)
    name =  db.Column(db.String(45), nullable = False)
    customer_id = db.Column(db.String(45),nullable = False)
    maps_url = db.Column(db.String(2048),nullable = False)
    x_coordinate = db.Column(db.Numeric(precision = 8, scale=5), nullable = False)
    y_coordinate = db.Column(db.Numeric(precision = 8, scale=5), nullable = False)
    address = db.Column(db.String(255))
    country = db.Column(db.String(45))
    state = db.Column(db.String(45))
    size = db.Column(INTEGER(unsigned=True), nullable = False )
    rooms = db.Column(INTEGER(unsigned=True), nullable = False )
    bathrooms = db.Column(INTEGER(unsigned=True), nullable = False )
    kitchens = db.Column(INTEGER(unsigned=True), nullable = False )

How can I make the Schema to represent the coordinates as a list containing the x_coordinate and the y_coordinate?
(newbie extra question). Is it a bad practice to use diferent variable names in the db model and in the Schema?

score 0 · Answer 1 · answered Feb 22 '21 at 09:00

Please try this (untested):

from marshmallow_sqlalchemy import field_for

[...]

coordinates = fields.Tuple(
    (field_for(Location, "x_coordinate"), field_for(Location, "y_coordinate"))
)

Not sure it is the best idea here because then you can't just cram the data loaded from the schema into the object init. But nothing prevents you from having an API (schemas) that differs from the DB representation.

How to define a marshamllow List field using marshmallow_sqlalchemy

1 Answers1