Using JSON Type with Flask-sqlalchemy & Postgresql

Looking at the SQLAlchemy documentation for the JSON data type it appears that you should be able to use the .cast method:

from sqlalchemy.types import Integer

from app import app, db
from models import Target 

# SQLAlchemy 1.1+
data = Target.query.order_by(Target.product['salesrank'].astext.cast(Integer))

# SQLAlchemy < 1
data = Target.query.order_by(Target.product['salesrank'].cast(Integer))