python---sqlalchemy(一)

2024-08-31 22:18
文章标签 python sqlalchemy

本文主要是介绍python---sqlalchemy(一),希望对大家解决编程问题提供一定的参考价值,需要的开发者们随着小编来一起学习吧!

      • 执行原生SQL语句
      • 创建删除表
      • 操作数据库表
      • scoped_session
      • 增删改查
      • 其他

执行原生SQL语句

import time
import threading
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.engine.base import Engineengine = create_engine("mysql+pymysql://root:root@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)
)def task(arg):# 方式一# conn = engine.raw_connection()# cursor = conn.cursor()# cursor.execute(#     "select * from user "# )# result = cursor.fetchall()# cursor.close()# conn.close()# print(result)# print("------ # 方式二----------------")# cur = engine.execute("select * from user")# result = cur.fetchall()# cur.close()# print(result)# print("------ # 方式三----------------")conn = engine.contextual_connect()with conn:cur = conn.execute("select * from user")result = cur.fetchall()print(result)for i in range(5):t = threading.Thread(target=task, args=(i,))t.start()

方式一输出如下:

(('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3))
(('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3))
(('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3))
(('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3))
(('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3))

方式二如下:

[('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3)]
[('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3)]
[('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3)]
[('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3)]
[('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3)]

方式三如下:

[('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3)]
[('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3)]
[('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3)]
[('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3)]
[('safly', '123', 1), ('saf', '123', 2), ('alex', '123', 3)]

创建删除表

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import datetime
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index
from 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):__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():"""根据类创建数据库表:return:"""engine = create_engine("mysql+pymysql://root:root@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:root@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.drop_all(engine)if __name__ == '__main__':drop_db()init_db()

操作数据库表

from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engineBase = declarative_base()
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'),)engine = create_engine("mysql+pymysql://root:root@127.0.0.1:3306/test", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)# 每次执行数据库操作时,都需要创建一个session
session = Session()# ############# 执行ORM操作 #############
obj1 = Users(name="safly1")
session.add(obj1)# 提交事务
session.commit()
# 关闭session
session.close()

scoped_session

from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_sessionimport datetime
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index
from sqlalchemy.orm import relationshipBase = declarative_base()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'),)engine = create_engine("mysql+pymysql://root:root@127.0.0.1:3306/test", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)"""
# 线程安全,基于本地线程实现每个线程用同一个session
# 特殊的:scoped_session中有原来方法的Session中的一下方法:"""
session = scoped_session(Session)# ############# 执行ORM操作 #############
obj1 = Users(name="safly")
session.add(obj1)# 提交事务
session.commit()
# 关闭session
session.close()

总结:

SQLAlchemy两种创建session的方式:方式一:import modelsfrom threading import Threadfrom sqlalchemy.orm import sessionmakerfrom sqlalchemy import create_engineengine =create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/s8day128db?charset=utf8",pool_size=2,max_overflow=0)XXXXXX = sessionmaker(bind=engine)def task():from sqlalchemy.orm.session import Sessionsession = XXXXXX()data = session.query(models.Classes).all()print(data)session.close()for i in range(10):t = Thread(target=task)t.start()方式二(推荐):import modelsfrom threading import Threadfrom sqlalchemy.orm import sessionmakerfrom sqlalchemy import create_enginefrom sqlalchemy.orm import scoped_sessionengine =create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/s8day128db?charset=utf8",pool_size=2,max_overflow=0)XXXXXX = sessionmaker(bind=engine)session = scoped_session(XXXXXX)def task():# 1. 原来的session对象 = 执行session.registry()# 2. 原来session对象.querydata = session.query(models.Classes).all()print(data)session.remove()for i in range(10):t = Thread(target=task)t.start()flask-session默认也是使用的第二种方式:scoped_session

增删改查

import datetime
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index
from sqlalchemy.orm import relationshipBase = declarative_base()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'),)from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
from sqlalchemy.sql import textengine = create_engine("mysql+pymysql://root:root@127.0.0.1:3306/test", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)session = Session()# ################ 添加add\add_all ################
"""
obj1 = Users(name="wupeiqi")
session.add(obj1)session.add_all([Users(name="wupeiqi"),Users(name="alex"),])
session.commit()
"""# ################ 删除 ################
"""
session.query(Users).filter(Users.id > 2).delete()
session.commit()"""# ################ 修改 ################"""
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()
"""
# ################ 查询 ################
"""
"""print("-------r1----------")
r1 = session.query(Users).all()for i in r1:print(i.name)print("-------r2----------")r2 = session.query(Users.name, Users.age).all()
for i in r2:print(i)print("-------r3----------")r3 = session.query(Users).filter(Users.name == "099099").all()for i in r3:print(i.name)print("-------r4----------")
r4 = session.query(Users).filter_by(name='099099').all()for i in r4:print(i.name)print("-------r5----------")
r5 = session.query(Users).filter_by(name='099099').first()print(r5.name)print("-------r6----------")
r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=5, name='099099').order_by(Users.id).all()
for i in r6:print(i.name)print("-------r7----------")
r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='099099').all()
for i in r7:print(i.name)session.close()

其他

import datetime
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index
from sqlalchemy.orm import relationshipBase = declarative_base()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)from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
from sqlalchemy.sql import textengine = create_engine("mysql+pymysql://root:root@127.0.0.1:3306/test", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)session = Session()################################   条件###############################
ret = session.query(Users).filter(Users.id > 1, Users.name == 'safly').all()ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == '099099').all()ret = session.query(Users).filter(Users.id.in_([1, 3, 4, 10])).all()ret = session.query(Users).filter(~Users.id.in_([1, 3, 4])).all()ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name='099099'))).all()from sqlalchemy import and_, or_ret = session.query(Users).filter(and_(Users.id > 3, Users.name == 'xiaowan')).all()ret = session.query(Users).filter(or_(Users.id > 11, Users.name == 'eric')).all()ret = session.query(Users).filter(or_(Users.id > 2,and_(Users.name == 'eric', Users.id > 3),Users.extra != "")).all()# ################################  通配符###############################
ret = session.query(Users).filter(Users.name.like('09%')).all()ret = session.query(Users).filter(~Users.name.like('09%')).all()#
# ############################### 切片###############################
ret = session.query(Users)[1:4]################################  排序###############################
ret = session.query(Users).order_by(Users.name.desc()).all()ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all()# ############################### 分组###############################
from sqlalchemy.sql import funcret = session.query(Users).group_by(Users.age).all()ret = session.query(func.max(Users.id),func.sum(Users.id),func.min(Users.id)).group_by(Users.name).all()ret = session.query(func.max(Users.id),func.sum(Users.id),func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) > 2).all()############################### 连表###############################
# (<__main__.Users object at 0x05934670>, <__main__.Hosts object at 0x05934530>)
# (<__main__.Users object at 0x05934610>, <__main__.Hosts object at 0x05934650>)
ret = session.query(Users, Hosts).filter(Users.id == Hosts.id).all()# for i in ret:
#     print(i)# ??
ret = session.query(Users).join(Hosts).all()
print(ret)
# ret = session.query(Users).join(Hosts, isouter=True).all()################################  组合###############################
# [('safly',), ('xiaowan',), ('sdfsf',), ('werwrw',), ('www',), ('wwerwerw',)]
q1 = session.query(Users.name).filter(Users.id > 2)
q2 = session.query(Hosts.name).filter(Hosts.id < 4)
ret = q1.union(q2).all()
print(ret)# [('safly',), ('xiaowan',), ('sdfsf',), ('werwrw',), ('www',), ('wwerwerw',), ('safly',)]
q1 = session.query(Users.name).filter(Users.id > 2)
q2 = session.query(Hosts.name).filter(Hosts.id < 4)
ret = q1.union_all(q2).all()
print(ret)session.close()

这篇关于python---sqlalchemy(一)的文章就介绍到这儿,希望我们推荐的文章对编程师们有所帮助!



http://www.chinasem.cn/article/1125141

相关文章

Python如何使用__slots__实现节省内存和性能优化

《Python如何使用__slots__实现节省内存和性能优化》你有想过,一个小小的__slots__能让你的Python类内存消耗直接减半吗,没错,今天咱们要聊的就是这个让人眼前一亮的技巧,感兴趣的... 目录背景:内存吃得满满的类__slots__:你的内存管理小助手举个大概的例子:看看效果如何?1.

Python+PyQt5实现多屏幕协同播放功能

《Python+PyQt5实现多屏幕协同播放功能》在现代会议展示、数字广告、展览展示等场景中,多屏幕协同播放已成为刚需,下面我们就来看看如何利用Python和PyQt5开发一套功能强大的跨屏播控系统吧... 目录一、项目概述:突破传统播放限制二、核心技术解析2.1 多屏管理机制2.2 播放引擎设计2.3 专

Python中随机休眠技术原理与应用详解

《Python中随机休眠技术原理与应用详解》在编程中,让程序暂停执行特定时间是常见需求,当需要引入不确定性时,随机休眠就成为关键技巧,下面我们就来看看Python中随机休眠技术的具体实现与应用吧... 目录引言一、实现原理与基础方法1.1 核心函数解析1.2 基础实现模板1.3 整数版实现二、典型应用场景2

Python实现无痛修改第三方库源码的方法详解

《Python实现无痛修改第三方库源码的方法详解》很多时候,我们下载的第三方库是不会有需求不满足的情况,但也有极少的情况,第三方库没有兼顾到需求,本文将介绍几个修改源码的操作,大家可以根据需求进行选择... 目录需求不符合模拟示例 1. 修改源文件2. 继承修改3. 猴子补丁4. 追踪局部变量需求不符合很

python+opencv处理颜色之将目标颜色转换实例代码

《python+opencv处理颜色之将目标颜色转换实例代码》OpenCV是一个的跨平台计算机视觉库,可以运行在Linux、Windows和MacOS操作系统上,:本文主要介绍python+ope... 目录下面是代码+ 效果 + 解释转HSV: 关于颜色总是要转HSV的掩膜再标注总结 目标:将红色的部分滤

Python 中的异步与同步深度解析(实践记录)

《Python中的异步与同步深度解析(实践记录)》在Python编程世界里,异步和同步的概念是理解程序执行流程和性能优化的关键,这篇文章将带你深入了解它们的差异,以及阻塞和非阻塞的特性,同时通过实际... 目录python中的异步与同步:深度解析与实践异步与同步的定义异步同步阻塞与非阻塞的概念阻塞非阻塞同步

Python Dash框架在数据可视化仪表板中的应用与实践记录

《PythonDash框架在数据可视化仪表板中的应用与实践记录》Python的PlotlyDash库提供了一种简便且强大的方式来构建和展示互动式数据仪表板,本篇文章将深入探讨如何使用Dash设计一... 目录python Dash框架在数据可视化仪表板中的应用与实践1. 什么是Plotly Dash?1.1

在C#中调用Python代码的两种实现方式

《在C#中调用Python代码的两种实现方式》:本文主要介绍在C#中调用Python代码的两种实现方式,具有很好的参考价值,希望对大家有所帮助,如有错误或未考虑完全的地方,望不吝赐教... 目录C#调用python代码的方式1. 使用 Python.NET2. 使用外部进程调用 Python 脚本总结C#调

Python下载Pandas包的步骤

《Python下载Pandas包的步骤》:本文主要介绍Python下载Pandas包的步骤,在python中安装pandas库,我采取的方法是用PIP的方法在Python目标位置进行安装,本文给大... 目录安装步骤1、首先找到我们安装python的目录2、使用命令行到Python安装目录下3、我们回到Py

Python GUI框架中的PyQt详解

《PythonGUI框架中的PyQt详解》PyQt是Python语言中最强大且广泛应用的GUI框架之一,基于Qt库的Python绑定实现,本文将深入解析PyQt的核心模块,并通过代码示例展示其应用场... 目录一、PyQt核心模块概览二、核心模块详解与示例1. QtCore - 核心基础模块2. QtWid