Python3 集成SQLAlchemy ORM 框架：实现简单增删改查功能封装

SQLAlchemy ORM 内部组件结构图及其说明：

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，将创建的类翻译为SQl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：

基于pymysql连接
    mysql+pymysql://:@/[?]

Python 基于SQLAlchemy 初始化表结构

import datetime
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime
from sqlalchemy.orm import relationship, sessionmaker

Base = declarative_base()
engine = create_engine(
    "mysql+pymysql://root:[email protected]:3306/hotel",
    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）
)
Session = sessionmaker(engine)

# ##################### 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):
    __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"))

    # 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 #########################

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():
    Base.metadata.create_all(engine)


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


if __name__ == '__main__':
    drop_db()
    init_db()

Python 基于SQLAlchemy 实现对表基础操作:增删改查

from orm import Users, Hosts, Session
# 原生SQL查询
from sqlalchemy.sql import text

# 全局session 实例化
session = Session()


# 简单插入
def insert():
    # ############# 执行ORM操作 #############
    obj1 = Users(name="alex1")
    session.add(obj1)
    # 提交事务
    session.commit()


# 批量插入
def batch_insert():
    session.add_all([
        Users(name="wupeiqi"),
        Users(name="alex"),
        Hosts(name="c1.com"),
    ])
    session.commit()


# 简单条件删除
def delete():
    session.query(Users).filter(Users.id > 2).delete()
    session.commit()


# 简单条件更新
def update():
    session.query(Users).filter(Users.id > 0).update({"name": "099"})
    session.query(Users).filter(Users.id > 0).update({Users.name: Users.name + "099"}, synchronize_session=False)
    session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate")
    session.commit()


# 简单查询
def select():
    r1 = session.query(Users).all()
    print(r1)
    r2 = session.query(Users.name.label('xx'), Users.age).all()
    print(r2)
    r3 = session.query(Users).filter(Users.name == "alex").all()
    print(r3)
    r4 = session.query(Users).filter_by(name='alex').all()
    print(r4)
    r5 = session.query(Users).filter_by(name='alex').first()
    print(r5)
    r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(
        Users.id).all()
    print(r6)
    r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all()
    print(r7)


# 全局session 关闭
session.close()

if __name__ == '__main__':
    # insert()
    # batch_insert()
    # delete()
    # update()
    select()