Is it possible to dynamically nest other schemas?

I have a MySQL table that has MANY relationships (about 50) and I would like to avoid:

• Include all relationships in nested items
• Write schemas for each case, depending on which relationship to nest

I tried setting the nested items in the WebsiteSchema constructor, setting it in the include_items() method, but nothing works, the items property only exists if it has been defined completely in the class definition. I tried searching in the docs and Google but I cannot find how to do this, I have a hunch I should be using the OPTIONS_CLASS but I don’t quite understand how it works.

Code showing what I tried:

from components.ma import ma
from schemas.item import ItemSchema

class WebsiteSchema(ma.SQLAlchemyAutoSchema):
    # This line works obviously
    # items = ma.Nested(ItemSchema, many=True)
    
    items = None

    # Not working
    def __init__(self, **kwargs):
        self.items = ma.Nested(ItemSchema, many=True)
        super().__init__(**kwargs)

    # Not working
    def include_items(self):
        self.items = ma.Nested(ItemSchema, many=True)

[NaturalBornCamper]

Thanks a million! from_dict with the extra Python theory I didn’t know about will be of tremendous help!

[sloria]

Oh, that was haste on my part. Since it looks like you’re using flask-marshmallow, then you can access the fields from ma. I also fixed the List(Nested(...)) usage. I updated my code snippet.