sqlalchemy写with语句 在SQLAlchemy中，可以使用`with`语句来管理数据库连接和事务的生命周期。下面是使用`with`语句的示例代码： ```python fromsqlalchemyimportcreate_engine fromsqlalchemy.ormimportsessionmaker #创建数据库引擎 engine=create_engine('数据库连接字符串') #创建一个会话工厂 Session=session...
the scoped_session() function is provided which produces a thread-managed registry of Session objects. It is commonly used in web applications so that a single global variable can be used to safely represent transactional sessions with sets of objects, localized to a single thread. using transacti...
withSession()assession: session.add(user) session.commit() Here the session is closed when the context manager block ends. And if an error occurs inside it, the session is rolled back. A variant of this pattern can be used to have a session that automatically commits at the end, while s...
from sqlalchemy.ormimportsessionmakerSession=sessionmaker(bind=engine)withSession()as session:#dosome database operations 1. 2. 3. 4. 5. 6. 这个例子中,我们使用sessionmaker创建了一个Session类,并在with语句中创建了一个Session实例。在with块中,我们可以执行任何数据库操作,而无需关心连接的管理。当wit...
with Session(engine) as session: result = session.execute(sql) for row in result: print(row.name, row.age) # liangshan 23 1. 2. 3. 4. 5. 6. 7. 现在结果与之前的结果: BEGIN (implicit) select name, age from users where age = 23; ...
commit() except Exception as e: session.rollback() raise e finally: session.close() 3.5 使用示例 import json from sqlalchemy import create_engine, and_, or_, update def queryRows(): """ 查询示例 """ with getSession() as session: query = session.query(YmUser).filter( or_( and_( ...
from sqlalchemy.orm import Session with Session(engine) as session: session.add(MyObject()) session.commit()此外,sessionmaker 对象支持一个 sessionmaker.begin() 上下文管理器,将在一个块中创建一个 Session 并开始/提交一个事务:from sqlalchemy.orm import sessionmaker Session = sessionmaker(engine) ...
with session.begin(): session.add(some_object()) session.add(some_other_object()) # 最后提交事务,如果有则回滚 # 是引发的异常 1. 2. 3. 4. 5. 在上述上下文结束时,假设没有引发异常,任何挂起的对象都将刷新到数据库并提交数据库事务。 如果在上述块中引发异常,则事务将回滚。 在这两种情况下,退...
session.commit() exception: session.rollback() finally: session.close() 二、说明 begin(),开始事务 with_for_update(),行级锁 commit(),提交事务,释放锁 rollback(),回滚,释放锁 close(),关闭会话,不释放锁 三、示例 1、业务 钱包表,两个用户钱包,用户1转账100给用户2。
with Session(engine) as sess: obj1 = sess.scalar( select(MyTable) .where(MyTable.id == 1) .execution_options( schema_translate_map={None: "test_schema"}, identity_token="test_schema", ) ) obj2 = sess.scalar( select(MyTable) .where(MyTable.id == 1) .execution_options( schema_...