from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session,sessionmaker
 
 
db_connect = "mysql+pymysql://root:password@localhost:3306/db_name?charset=utf8"
 
create=create_engine(db_connect)
SessionType=scoped_session(sessionmaker(bind=create,expire_on_commit=False))
 
def GetSession():
    return SessionType()
 
from contextlib import contextmanager
 
@contextmanager
def session_socpe():
    session=GetSession()
    try:
        yield session
        session.commit()
    except:
        session.rollback()
        raise
    finally:
        session.close()

with session_socpe() as session:
    obj = session.query(Model类).filter(Model类.字段==参数).first()

with session_socpe() as session:
    obj = Model类(字段1=值1, 字段2=值2, 字段3=值3)
    session.add(obj)

with session_socpe() as session:
　　obj = session.query(Model类).filter(Model类.字段==参数).delete()

with session_socpe() as session:
　　obj = session.query(Model类).filter(Model类.字段==参数).update({"修改字段":"修改值"})