db.session.query() 从整个会话进度去查询数据，commit数据，基于session.query均可以查询
db.session.commit()数据会刷新到数据库中，但是没有更新模型数据，即mode.query查不到刚才commit的相关数据
问题解决
sqlalchemy.orm.exc.DetachedInstanceError: Instance <EntityMedicamentVariety at 0x2675fef6978> is not bound to a Session; attribute refresh operation cannot proceed (Ba
ckground on this error at: http://sqlalche.me/e/bhk3)分析：
commit后，会将session内所有对象进行提交并删除，后续session内无对象，需要手动add。
SQlAlchemy的ORM方式将数据库的记录映射成用户定义好的模型类，这些类对象的实例只在数据库的session生命期内有效，若关闭session，在访问此类的对象实例，就会报错。
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class User(Base):
__tablename__ = 'USER'
id = Column(Integer, Sequence('USER_SEQ'), primary_key=True, autoincrement=True)
name = Column(String(30))
age = Column(Integer)
status = Column(String(30))
engine = create_engine(str(db_url), encoding=b'utf-8', echo=echo, convert_unicode=True)
Session = sessionmaker(bind=engine)
session = Session()
user = User(name='John', age=30)
session.add(user)
session.commit()
session.close()
print user.name
Traceback (most recent call last):
File "E:\WorkCopy\test\test.py", line 21, in test_something
print user.name
File "C:\Python27\lib\site-packages\sqlalchemy\orm\attributes.py", line 237, in __get__
return self.impl.get(instance_state(instance), dict_)
File "C:\Python27\lib\site-packages\sqlalchemy\orm\attributes.py", line 573, in get
value = state._load_expired(state, passive)
File "C:\Python27\lib\site-packages\sqlalchemy\orm\state.py", line 480, in _load_expired
self.manager.deferred_scalar_loader(self, toload)
File "C:\Python27\lib\site-packages\sqlalchemy\orm\loading.py", line 610, in load_scalar_attributes
(state_str(state)))
DetachedInstanceError: Instance <User at 0x32768d0> is not bound to a Session; attribute refresh operation cannot proceed关闭session后，如何继续使用此对象，使用session.expunge()
user = User(name='John', age=30)
session.add(user)
session.commit()
session.refresh(user)
session.expunge(user)
session.close()
print user.name
使用 session.refresh(user) 是为了读取自增字段值（如果有的话）到 user 对象