这只是个例子我建议你阅读更多关于context manager和decorators在python中的内容。真的很有帮助

from contextlib import contextmanager
from sqlalchemy import create_engine
from sqlalchemy.orm import Session, declarative_base, sessionmaker

class SqlAlchemy:
    def __init__(self, database_url: str):
        self.engine = create_engine(database_url, echo=False)
        self.session = sessionmaker(self.engine)
        self.base = declarative_base()

@contextmanager
def in_transaction(session) -> Session:
    session = session()
    session.begin()
    try:
        yield session
        session.commit()
    except BaseException:
        session.rollback()
        raise
    finally:
        session.close()

db = SqlAlchemy('your database url')

def db_session(db):
    with in_transaction(db.session) as session:
        yield session
        
        
# example function where you need session
@db_session
def my_function(session):
    session.execute('SQL for example:)')

你能提供更多的信息吗？

• 您使用哪些信息来确定会话已关闭？
• 如果有的话，你的程序有什么输出？（例如错误消息或SQL语句）
• 否则代码会工作吗？即，表是否成功删除？

另外，启用 sqlalchemy engine echo logging功能：

engine = create_engine(connection_string, echo=True)

例如，当我运行与你的代码非常相似的代码时（我试图删除"foo"），我得到以下输出：

2023-06-28 08:26:03,673 INFO sqlalchemy.engine.Engine select pg_catalog.version()
2023-06-28 08:26:03,673 INFO sqlalchemy.engine.Engine [raw sql] {}
2023-06-28 08:26:03,674 INFO sqlalchemy.engine.Engine select current_schema()
2023-06-28 08:26:03,674 INFO sqlalchemy.engine.Engine [raw sql] {}
2023-06-28 08:26:03,679 INFO sqlalchemy.engine.Engine show standard_conforming_strings
2023-06-28 08:26:03,679 INFO sqlalchemy.engine.Engine [raw sql] {}
2023-06-28 08:26:03,686 INFO sqlalchemy.engine.Engine BEGIN (implicit)
2023-06-28 08:26:03,686 INFO sqlalchemy.engine.Engine DROP TABLE IF EXISTS foo;
2023-06-28 08:26:03,686 INFO sqlalchemy.engine.Engine [generated in 0.00021s] {}
2023-06-28 08:26:03,688 INFO sqlalchemy.engine.Engine ROLLBACK
Error occurred while executing SQL commands: This transaction is inactive
/home/nchappell/programming/py/foo/foo.py:21: SAWarning: transaction already deassociated from connection
  session.rollback()

从BEGIN (implicit)及以下的一切都很有趣，并告诉我程序配置不正确。请分享更多信息，我可以尝试帮助你。