Hi
Newbie here. I think I have a fundamental misunderstanding of either how
session works or you inspect works. My goal is to track changes to my
object. I wrote up this sample to show what I'm having trouble
understanding.
from sqlalchemy import create_engine, inspect
from sqlalchemy import Column, BigInteger, String, Date, Integer
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from dateutil.relativedelta import *
Base = declarative_base()
class SaTest(Base):
__tablename__ = 'sa_test'
id = Column(BigInteger, primary_key=True)
name = Column(String(50))
dob = Column(Date)
number_of_children = Column(Integer)
def __repr__(self):
return self.name
engine =
create_engine('mysql://mysqluser:mysqlpassword@servername/databasename')
Base.metadata.bind = engine
DBSession = sessionmaker(bind=engine)
session = DBSession()
"""
# run this the first time to create the data
jim = SaTest(name='Jim', dob=parse('1971-02-23'), number_of_children=3)
session.add(jim)
joe = SaTest(name='Joe', dob=parse('1968-06-09'), number_of_children=5)
session.add(joe)
session.commit()
"""
jim = session.query(SaTest).filter_by(id=1).one()
jim.dob = jim.dob + relativedelta(days=+14)
jim.number_of_children = jim.number_of_children + 1
#joe = session.query(SaTest).filter_by(id=2).first() <---- if I
uncomment this line, inspect doesn't display the changes in history
insp = inspect(jim)
for attr, attr_state in insp.attrs.items():
if attr_state.history.has_changes():
print('{}: {}'.format(attr, attr_state.value))
print('History: {}\n'.format(attr_state.history))
I've built this based on the example at the bottom of page 107 in the
O'Reilly Essential SQLAlchemy book.
It seems to my that running the second query is somehow invalidating the
inspection of the jim object. I'd really like to understand why, but
haven't been able to find anything to help explain it to me.
Any help would really be appreciated.
-Jim
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