from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, Numeric
from sqlalchemy.ext.hybrid import hybrid_property
from sqlalchemy import create_engine
from sqlalchemy.orm import Session

Base = declarative_base()

class BankAccount(Base):
    __tablename__ = 'bank_account'
    id = Column(Integer, primary_key=True)

    balance = Column(Numeric)
    pending = Column(Numeric)

    @hybrid_property
    def total(self):
        return self.balance + self.pending

print BankAccount(balance=1000, pending=500).total

engine = create_engine('sqlite://', echo=True)
Base.metadata.create_all(engine)

session = Session(engine)
session.add_all([
    BankAccount(balance=4000, pending=500),
    BankAccount(balance=10000, pending=0),
])
session.commit()

print session.query(BankAccount.total).filter(BankAccount.total.between(3000, 5000)).all()


myaccount = session.query(BankAccount).first()
print myaccount.total