SQLAlchemy“采用简单的Python语言，为高效和高性能的数据库访问设计，实现了完整的企业级持久模型”。SQLAlchemy的理念是，SQL数据库的量级和性能重要于对象集合；而对象集合的抽象又重要于表和行。因此，SQLAlchmey采用了类似于Java里Hibernate的数据映射模型，而不是其他ORM框架采用的Active Record模型。不过，Elixir和declarative等可选插件可以让用户使用声明语法。

安装

pip3 install SQLAlchemy

pip3 install pymysql  #需要pymysql或者MySQLdb的支持

连接数据库

mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]

下面我们看一个例子：

#导入想关模块
from sqlalchemy import create_engine  
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker, relationship

engine = create_engine("mysql+pymysql://root:123456@192.168.11.12:3306/haha", encoding='utf-8', max_overflow=5)

# DBSession = sessionmaker(bind=engine)
#实例化
Base = declarative_base()


# 主机表
class Host(Base):        #声明类
    __tablename__ = 'host'  #需要创建的表名
    nid = Column(Integer, primary_key=True, autoincrement=True)　　#定义主键，自增1 ，其实这里还可以有其他参数
    hostname = Column(String(32))
    ip = Column(String(32), unique=True)
    port = Column(String(32))
    host_user = relationship('HostUser',secondary=lambda: HostToHostUser.__table__,backref='h')#映射表的外键


# 主机用户表
class HostUser(Base):
    __tablename__ = 'host_user'
    nid = Column(Integer, primary_key=True, autoincrement=True)
    username = Column(String(32))
    passwd = Column(String(32))


# 主机用户与主机关系表
class HostToHostUser(Base):
    __tablename__ = 'host_to_hostuser'
    nid = Column(Integer, primary_key=True, autoincrement=True)
    user_nid = Column(Integer, ForeignKey('host_user.nid'))
    host_nid = Column(Integer, ForeignKey('host.nid'))
    host = relationship('Host', backref='h')
    host_user = relationship('HostUser', backref='u')


# 审计表
class AuditLog(Base):
    __tablename__ = 'audit_log'
    nid = Column(Integer, primary_key=True)
    user_nid = Column(Integer, ForeignKey('host_user.nid'))
    host_nid = Column(Integer, ForeignKey('host.nid'))
    cmd = Column(String(255))
    date = Column(String(255))


def init_db():
    Base.metadata.create_all(engine)


def drop_db():
    Base.metadata.drop_all(engine)


init_db()

Session = sessionmaker(bind=engine)
session = Session()
#
#


session.add_all((
    Host(hostname='web1', ip='192.168.11.12', port='22', ),
    Host(hostname='web2', ip='192.168.11.23', port='22', ),
    Host(hostname='web3', ip='192.168.11.34', port='22', ),
    Host(hostname='web4', ip='192.168.11.45', port='22', ),
    Host(hostname='web5', ip='192.168.11.228', port='22', ),
))
session.commit()

session.add_all([
    HostUser(username='madking', passwd='123', ),
    HostUser(username='oldboy', passwd='123', ),
])
session.commit()

session.add_all((
    HostToHostUser(user_nid='1', host_nid='1', ),
    HostToHostUser(user_nid='1', host_nid='2', ),
    HostToHostUser(user_nid='1', host_nid='5', ),
    HostToHostUser(user_nid='2', host_nid='1', ),
))
session.commit()