1 from sqlalchemy import *
2 from sqlalchemy.orm import *
3
4 metadata = MetaData()
5
6 t = Table(
7 't', metadata,
8 Column('id', Integer, primary_key=True),
9 Column('state', String(10)),
10 )
11
12 class Model(object): pass
13
14 mapper(Model, t)
15
16 engine = create_engine('sqlite://')
17 metadata.create_all(engine)
18
19 session = sessionmaker(bind=engine)()
20
21 obj1 = Model()
22 obj1.state = 'value1'
23 session.add(obj1)
24 session.commit()
25 obj_id = obj1.id
26
27 obj2 = Model()
28 obj2.id = obj_id
29 obj2.state = 'value2'
30 obj3 = session.merge(obj2)
31 session.commit()
32 print obj3 is obj1, obj3 is obj2
33 print obj3.state
结果：
True False
value2
1 from sqlalchemy import *
2 from sqlalchemy.orm import *
3
4 metadata = MetaData()
5
6 t = Table(
7 't', metadata,
8 Column('id', Integer, primary_key=True),
9 Column('state1', String(10)),
10 Column('state2', String(10)),
11 )
12
13 class Model(object): pass
14
15 mapper(Model, t)
16
17 engine = create_engine('sqlite://')
18 metadata.create_all(engine)
19
20 session = sessionmaker(bind=engine)()
21
22 obj1 = Model()
23 obj1.state1 = 'value1-1'
24 obj1.state2 = 'value2-1'
25 session.add(obj1)
26 session.commit()
27 obj_id = obj1.id
28 session.expunge_all()
29
30 obj2 = Model()
31 obj2.id = obj_id
32 obj2.state1 = 'value1-2'
33 obj3 = session.merge(obj2)
34 session.commit()
35 print obj3 is obj1, obj3 is obj2
36 print obj3.state1, obj3.state2
结果：
False False
value1-2 value2-1
来源：https://www.cnblogs.com/haojinming/archive/2013/04/16/3024936.html