SQLAlchemy add datetime column with integer column converted to minute interval [duplicate]

I had similar problem and didn't found way to convert integer to postgresql interval. I resolved this problem by changing column type from Integer to INTERVAL like this:

from datetime import datetime, timedelta
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, DateTime, create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.dialects.postgresql import INTERVAL
from config import DB_CONFIG

Base = declarative_base()


class Model(Base):

    __tablename__ = 'model'
    id = Column(Integer, primary_key=True)
    column_a = Column(DateTime)
    column_b = Column(INTERVAL)


engine = create_engine(
    'postgresql+psycopg2://%s:%s@%s:%d/%s'
    % (DB_CONFIG["user"], DB_CONFIG["password"], DB_CONFIG["host"], 
       DB_CONFIG["port"], DB_CONFIG["db_name"]),
    echo=True
)
Session = sessionmaker(bind=engine)
session = Session()

Base.metadata.create_all(engine)

# INTERVAL type can be set via instance of timedelta
session.add(Model(column_a=datetime.now(), column_b=timedelta(minutes=10)))
session.add(Model(
    column_a=datetime.now() - timedelta(minutes=20),
    column_b=timedelta(minutes=10)
))
session.commit()

result = session.query(Model).filter(
    Model.column_a + Model.column_b > datetime.now()
).all()

for row in result:
    print row.id

Output after first run will be: 1