Updating models with SQLAlchemy

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A frequent operation in REST APIs is the "upsert", or "update or insert".

This is an idempotent operation where we send the data we want the API to store. If the data identifier already exists, an update is done. If it doesn't, it is created.

This idempotency is frequently seen with PUT requests. You can see it in action here:

resources/item.py

@blp.arguments(ItemUpdateSchema)
@blp.response(200, ItemSchema)
def put(self, item_data, item_id):
    item = ItemModel.query.get(item_id)
    if item:
        item.price = item_data["price"]
        item.name = item_data["name"]
    else:
        item = ItemModel(id=item_id, **item_data)

    db.session.add(item)
    db.session.commit()

    return item