SQLAlchemy
1.1.SQLAlchemy介绍
SQLAlchemy是一个基于Python实现的ORM框架。该框架建立在 DB API之上，使用关系对象映射进行数据库操作，简言之便是：将类和对象转换成SQL，然后使用数据API执行SQL并获取执行结果。
安装
pip install sqlalchemy
组成部分
Engine，框架的引擎Connection Pooling ，数据库连接池Dialect，选择连接数据库的DB API种类Schema/Types，架构和类型SQL Exprression Language，SQL表达式语言
SQLAlchemy本身无法操作数据库，其必须以来pymsql等第三方插件，Dialect用于和数据API进行交流，根据配置文件的不同调用不同的数据库API，从而实现对数据库的操作，如：
MySQL-Python mysql+mysqldb://: @ [: ]/ pymysql mysql+pymysql:// : @ / [? ] MySQL-Connector mysql+mysqlconnector:// : @ [: ]/ cx_Oracle oracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...] 更多：http://docs.sqlalchemy.org/en/latest/dialects/index.html
1.2.SQLAlchemy表结构
（1）创建单表
import datetimefrom sqlalchemy import create_enginefrom sqlalchemy.ext.declarative import declarative_basefrom sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, IndexBase = declarative_base()class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=False) email = Column(String(32), unique=True) ctime = Column(DateTime, default=datetime.datetime.now) extra = Column(Text, nullable=True) __table_args__ = ( UniqueConstraint('id', 'name', name='uix_id_name'), #id和name联合唯一 Index('ix_id_name', 'name', 'email'), #索引 )def init_db(): """ 根据类创建数据库表 :return: """ engine = create_engine( "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, # 超过连接池大小外最多创建的连接 pool_size=5, # 连接池大小 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 pool_recycle=-1 # 多久之后对线程池中的线程进行一次连接的回收（重置） ) Base.metadata.create_all(engine)def drop_db(): """ 根据类删除数据库表 :return: """ engine = create_engine( "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, # 超过连接池大小外最多创建的连接 pool_size=5, # 连接池大小 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 pool_recycle=-1 # 多久之后对线程池中的线程进行一次连接的回收（重置） ) Base.metadata.drop_all(engine)if __name__ == '__main__': drop_db() init_db() （2）创建多个表（包含FK，M2M关系）
import datetimefrom sqlalchemy import create_enginefrom sqlalchemy.ext.declarative import declarative_basefrom sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Indexfrom sqlalchemy.orm import relationshipBase = declarative_base()# ##################### 单表示例 #########################class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String(32), index=True) age = Column(Integer, default=18) email = Column(String(32), unique=True) ctime = Column(DateTime, default=datetime.datetime.now) extra = Column(Text, nullable=True) __table_args__ = ( # UniqueConstraint('id', 'name', name='uix_id_name'), # Index('ix_id_name', 'name', 'extra'), )class Hosts(Base): __tablename__ = 'hosts' id = Column(Integer, primary_key=True) name = Column(String(32), index=True) ctime = Column(DateTime, default=datetime.datetime.now)# ##################### 一对多示例 #########################class Hobby(Base): '''爱好''' __tablename__ = 'hobby' id = Column(Integer, primary_key=True) caption = Column(String(50), default='篮球')class Person(Base): __tablename__ = 'person' nid = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=True) hobby_id = Column(Integer, ForeignKey("hobby.id")) #hobby指的__tablename__ = 'hobby'，而不是类名Hobby # 与生成表结构无关，仅用于查询方便 hobby = relationship("Hobby", backref='pers')# ##################### 多对多示例 ##########################第三张表要自己生成class Server2Group(Base): __tablename__ = 'server2group' id = Column(Integer, primary_key=True, autoincrement=True) server_id = Column(Integer, ForeignKey('server.id')) group_id = Column(Integer, ForeignKey('group.id'))class Group(Base): __tablename__ = 'group' id = Column(Integer, primary_key=True) name = Column(String(64), unique=True, nullable=False) # 与生成表结构无关，仅用于查询方便 servers = relationship('Server', secondary='server2group', backref='groups')class Server(Base): __tablename__ = 'server' id = Column(Integer, primary_key=True, autoincrement=True) hostname = Column(String(64), unique=True, nullable=False)def init_db(): """ 根据类创建数据库表 :return: """ engine = create_engine( "mysql+pymysql://root:123456@127.0.0.1:3306/test?charset=utf8", max_overflow=0, # 超过连接池大小外最多创建的连接 pool_size=5, # 连接池大小 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 pool_recycle=-1 # 多久之后对线程池中的线程进行一次连接的回收（重置） ) Base.metadata.create_all(engine)def drop_db(): """ 根据类删除数据库表 :return: """ engine = create_engine( "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, # 超过连接池大小外最多创建的连接 pool_size=5, # 连接池大小 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 pool_recycle=-1 # 多久之后对线程池中的线程进行一次连接的回收（重置） ) Base.metadata.drop_all(engine)if __name__ == '__main__': drop_db() init_db() 实例：
models.py
import datetimefrom sqlalchemy import create_enginefrom sqlalchemy.ext.declarative import declarative_basefrom sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Indexfrom sqlalchemy.orm import relationshipBase = declarative_base()# ##################### 单表示例 #########################class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String(32), index=True) age = Column(Integer, default=18) email = Column(String(32), unique=True) ctime = Column(DateTime, default=datetime.datetime.now) extra = Column(Text, nullable=True) __table_args__ = ( # UniqueConstraint('id', 'name', name='uix_id_name'), # Index('ix_id_name', 'name', 'extra'), )class Hosts(Base): __tablename__ = 'hosts' id = Column(Integer, primary_key=True) name = Column(String(32), index=True) ctime = Column(DateTime, default=datetime.datetime.now)# ##################### 一对多示例 #########################class Hobby(Base): '''爱好''' __tablename__ = 'hobby' id = Column(Integer, primary_key=True) caption = Column(String(50), default='篮球')class Person(Base): __tablename__ = 'person' nid = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=True) hobby_id = Column(Integer, ForeignKey("hobby.id")) #hobby指的__tablename__ = 'hobby'，而不是类名Hobby # 与生成表结构无关，仅用于查询方便 hobby = relationship("Hobby", backref='pers')# ##################### 多对多示例 ##########################第三张表要自己生成class Server2Group(Base): __tablename__ = 'server2group' id = Column(Integer, primary_key=True, autoincrement=True) server_id = Column(Integer, ForeignKey('server.id')) group_id = Column(Integer, ForeignKey('group.id'))class Group(Base): __tablename__ = 'group' id = Column(Integer, primary_key=True) name = Column(String(64), unique=True, nullable=False) # 与生成表结构无关，仅用于查询方便 servers = relationship('Server', secondary='server2group', backref='groups')class Server(Base): __tablename__ = 'server' id = Column(Integer, primary_key=True, autoincrement=True) hostname = Column(String(64), unique=True, nullable=False)if __name__ == '__main__': engine = create_engine( "mysql+pymysql://root:123456@127.0.0.1:3306/test?charset=utf8", max_overflow=0, # 超过连接池大小外最多创建的连接 pool_size=5, # 连接池大小 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 pool_recycle=-1 # 多久之后对线程池中的线程进行一次连接的回收（重置） ) Base.metadata.create_all(engine) #创建 # Base.metadata.drop_all(engine) #删除
1.3.SQLAlchemy两种连接方式
第一种
from sqlalchemy.orm import sessionmakerfrom sqlalchemy import create_engineimport models#1.创建连接池engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/test?charset=utf8", max_overflow=0, pool_size=5)Session = sessionmaker(bind=engine)#2.从连接池中获取数据库连接session = Session()#3.执行ORM操作obj1 = models.Users(name="derek",email='derek@163.com')session.add(obj1)# 提交事务session.commit()# 4.关闭数据库连接(将连接放回连接池)session.close() 
第二种、基于scoped_session实现线程安全
首先导入，然后只要修改session = scoped_session(Session)
from sqlalchemy.orm import sessionmakerfrom sqlalchemy import create_enginefrom sqlalchemy.orm import scoped_sessionimport models#1.创建连接池engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/test?charset=utf8", max_overflow=0, pool_size=5)Session = sessionmaker(bind=engine)#2.从连接池中获取数据库连接# session = Session()session = scoped_session(Session)#3.执行ORM操作obj1 = models.Users(name="jack",email='jack@163.com')session.add(obj1)# 提交事务session.commit()# 4.关闭数据库连接session.close() 
1.4.增加数据
from sqlalchemy.orm import sessionmakerfrom sqlalchemy import create_enginefrom sqlalchemy.orm import scoped_sessionimport models#1.创建连接池engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/test?charset=utf8", max_overflow=0, pool_size=5)Session = sessionmaker(bind=engine)#2.从连接池中获取数据库连接session = Session()# session = scoped_session(Session)# #3.执行ORM操作# obj1 = models.Users(name="jack",email='jack@163.com')# session.add(obj1)# # 提交事务# session.commit()#批量增加,里面是列表session.add_all([ models.Users(name="jack1",email='jack1@163.com'), models.Users(name="jack2",email='jack2@163.com'),])session.commit()# 4.关闭数据库连接session.close()
1.5.查看和删除数据
#查看数据user_list = session.query(models.Users).all()for row in user_list: print(row.id) print(row.name) print(row.email) print(row.ctime)
from sqlalchemy.orm import sessionmakerfrom sqlalchemy import create_enginefrom sqlalchemy.orm import scoped_sessionimport models#1.创建连接池engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/test?charset=utf8", max_overflow=0, pool_size=5)Session = sessionmaker(bind=engine)#2.从连接池中获取数据库连接session = Session()# session = scoped_session(Session)# #3.执行ORM操作# obj1 = models.Users(name="jack",email='jack@163.com')# session.add(obj1)# # 提交事务# session.commit()# #批量增加,里面是列表# session.add_all([# models.Users(name="jack1",email='jack1@163.com'),# models.Users(name="jack2",email='jack2@163.com'),# ])# session.commit()#查看数据user_list = session.query(models.Users).all()for row in user_list: print(row.id) print(row.name) print(row.email) print(row.ctime)# 4.关闭数据库连接session.close() 查看的结果：
添加过滤条件
user_list = session.query(models.Users).filter(models.Users.id > 2) #id大于2的
删除数据
#删除数据session.query(models.Users).filter(models.Users.id > 4).delete()session.commit()
from sqlalchemy.orm import sessionmakerfrom sqlalchemy import create_enginefrom sqlalchemy.orm import scoped_sessionimport models#1.创建连接池engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/test?charset=utf8", max_overflow=0, pool_size=5)Session = sessionmaker(bind=engine)#2.从连接池中获取数据库连接session = Session()# session = scoped_session(Session)# #3.执行ORM操作# obj1 = models.Users(name="jack",email='jack@163.com')# session.add(obj1)# # 提交事务# session.commit()# #批量增加,里面是列表# session.add_all([# models.Users(name="jack1",email='jack1@163.com'),# models.Users(name="jack2",email='jack2@163.com'),# ])# session.commit()#查看数据# user_list = session.query(models.Users).all()# user_list = session.query(models.Users).filter(models.Users.id > 2) #id大于2的# for row in user_list:# print(row.id)# print(row.name)# print(row.email)# print(row.ctime)#删除数据session.query(models.Users).filter(models.Users.id > 4).delete()session.commit()# 4.关闭数据库连接session.close()
1.6.修改数据
#修改数据session.query(models.Users).filter(models.Users.id == 4).update({ 'name':'Tom'})session.query(models.Users).filter(models.Users.id == 1).update({ 'name': models.Users.name + "099"}, synchronize_session=False)session.query(models.Users).filter(models.Users.id == 3).update({ "age": models.Users.age + 1}, synchronize_session="evaluate") session.commit() 
结果：
