# coding=utf-8
    from sqlalchemy import Column, Integer, String, BigInteger
    from sqlalchemy.ext.declarative import declarative_base
    Base = declarative_base()


    class User(Base):

        __tablename__ = 'users'

        id = Column(Integer(), primary_key=True)
        username = Column(String(30), unique=True, nullable=False)
        password = Column(String, default='123456', nullable=False)
        name = Column(String(30), nullable=False)
        grade = Column(String(30))
        emp_no = Column(BigInteger, unique=True, nullable=False)

    print User.__table__


    from sqlalchemy import create_engine
    from sqlalchemy.orm import sessionmaker
    from sqlalchemy.ext.declarative import declarative_base


    Base = declarative_base()
    Session = sessionmaker()
    engine = create_engine('sqlite:///:memory:', echo=True)
    Session.configure(bind=engine)
    session = Session()
    Base.metadata.create_all(engine)

    ed_user = User(name='ed', username='jack', password='123', emp_no=1, grade='1')
    #
    session.add(ed_user)
    #
    with session.no_autoflush:
       session.query(User).filter_by(name='ed').first()

/usr/bin/python2.7 /home/pajamas/PycharmProjects/untitled5/data_generator.py
    users
    2017-07-30 17:56:28,903 INFO sqlalchemy.engine.base.Engine SELECT CAST('test plain returns' AS VARCHAR(60)) AS anon_1
    2017-07-30 17:56:28,904 INFO sqlalchemy.engine.base.Engine ()
    2017-07-30 17:56:28,904 INFO sqlalchemy.engine.base.Engine SELECT CAST('test unicode returns' AS VARCHAR(60)) AS anon_1
    2017-07-30 17:56:28,904 INFO sqlalchemy.engine.base.Engine ()
    2017-07-30 17:56:28,908 INFO sqlalchemy.engine.base.Engine BEGIN (implicit)
    sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such table: users [SQL: u'SELECT users.id AS users_id, users.username AS users_username, users.password AS users_password, users.name AS users_name, users.grade AS users_grade, users.emp_no AS users_emp_no nFROM users nWHERE users.name = ?n LIMIT ? OFFSET ?'] [parameters: ('ed', 1, 0)]
    2017-07-30 17:56:28,909 INFO sqlalchemy.engine.base.Engine SELECT users.id AS users_id, users.username AS users_username, users.password AS users_password, users.name AS users_name, users.grade AS users_grade, users.emp_no AS users_emp_no
    FROM users
    WHERE users.name = ?
    LIMIT ? OFFSET ?
    2017-07-30 17:56:28,909 INFO sqlalchemy.engine.base.Engine ('ed', 1, 0)

    Process finished with exit code 1

Base = declarative_base()
Session = sessionmaker()
engine = create_engine('sqlite:///:memory:', echo=True)