pyMysql

2023-01-09 08:47:43

本篇对于Python操作MySQL主要使用两种方式：

  • 原生模块 pymsql
  • ORM框架 SQLAchemy

pymsql

pymsql是Python中操作MySQL的模块，其使用方法和MySQLdb几乎相同。

下载安装

pip3 install pymysql

使用操作：

1，执行sql

#!/usr/bin/env python

# -*- coding:utf-8 -*-

import pymysql

# 创建连接

conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')

# 创建游标

cursor = conn.cursor()

# 执行SQL，并返回收影响行数

effect_row = cursor.execute("update hosts set host = '1.1.1.2'")

# 执行SQL，并返回受影响行数

#effect_row = cursor.execute("update hosts set host = '1.1.1.2' where nid > %s", (1,))

# 执行SQL，并返回受影响行数

#effect_row = cursor.executemany("insert into hosts(host,color_id)values(%s,%s)", [("1.1.1.11",1),("1.1.1.11",2)])

# 提交，不然无法保存新建或者修改的数据

conn.commit()

# 关闭游标

cursor.close()

# 关闭连接

conn.close()

2 获取新创建自增id

#!/usr/bin/env python

# -*- coding:utf-8 -*-

import pymysql

conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')

cursor = conn.cursor()

cursor.executemany("insert into hosts(host,color_id)values(%s,%s)", [("1.1.1.11",1),("1.1.1.11",2)])

conn.commit()

cursor.close()

conn.close()

# 获取最新自增ID

new_id = cursor.lastrowid

3，获取查询数据

#!/usr/bin/env python

# -*- coding:utf-8 -*-

import pymysql

conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')

cursor = conn.cursor()

cursor.execute("select * from hosts")

# 获取第一行数据

row_1 = cursor.fetchone()

# 获取前n行数据

# row_2 = cursor.fetchmany(3)

# 获取所有数据

# row_3 = cursor.fetchall()

conn.commit()

cursor.close()

conn.close()

注：在fetch数据时按照顺序进行，可以使用cursor.scroll(num,mode)来移动游标位置，如：

  • cursor.scroll(1,mode='relative')  # 相对当前位置移动
  • cursor.scroll(2,mode='absolute') # 相对绝对位置移动

4、fetch数据类型

　　关于默认获取的数据是元祖类型，如果想要或者字典类型的数据，即：

#!/usr/bin/env python

# -*- coding:utf-8 -*-

import pymysql

conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')

# 游标设置为字典类型

cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)

r = cursor.execute("call p1()")

result = cursor.fetchone()

conn.commit()

cursor.close()

conn.close()

SQLAchemy

SQLAlchemy是Python编程语言下的一款ORM框架，该框架建立在数据库API之上，使用关系对象映射进行数据库操作，简言之便是：将对象转换成SQL，然后使用数据API执行SQL并获取执行结果。

安装：

pip3 install SQLAlchemy

pyMysql

二、ORM功能使用

使用 ORM/Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 所有组件对数据进行操作。根据类创建对象，对象转换成SQL，执行SQL。

1，创建表

#!/usr/bin/env python

# -*- coding:utf-8 -*-

from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index

from sqlalchemy.orm import sessionmaker, relationship

from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5)

Base = declarative_base()

# 创建单表

class Users(Base):

    __tablename__ = 'users'

    id = Column(Integer, primary_key=True)

    name = Column(String(32))

    extra = Column(String(16))

    __table_args__ = (

    UniqueConstraint('id', 'name', name='uix_id_name'),

        Index('ix_id_name', 'name', 'extra'),

    )

# 一对多

class Favor(Base):

    __tablename__ = 'favor'

    nid = Column(Integer, primary_key=True)

    caption = Column(String(50), default='red', unique=True)

class Person(Base):

    __tablename__ = 'person'

    nid = Column(Integer, primary_key=True)

    name = Column(String(32), index=True, nullable=True)

    favor_id = Column(Integer, ForeignKey("favor.nid"))

# 多对多

class Group(Base):

    __tablename__ = 'group'

    id = Column(Integer, primary_key=True)

    name = Column(String(64), unique=True, nullable=False)

    port = Column(Integer, default=22)

class Server(Base):

    __tablename__ = 'server'

    id = Column(Integer, primary_key=True, autoincrement=True)

    hostname = Column(String(64), unique=True, nullable=False)

class ServerToGroup(Base):

    __tablename__ = 'servertogroup'

    nid = Column(Integer, primary_key=True, autoincrement=True)

    server_id = Column(Integer, ForeignKey('server.id'))

    group_id = Column(Integer, ForeignKey('group.id'))

def init_db():

    Base.metadata.create_all(engine)

def drop_db():

    Base.metadata.drop_all(engine)

注：设置外检的另一种方式 ForeignKeyConstraint(['other_id'], ['othertable.other_id'])

#!/usr/bin/env/python

# -*- coding:utf-8 -*-

from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy import Column,Integer,String,ForeignKey,UniqueConstraint,Index

from sqlalchemy.orm import  sessionmaker,relationship

from sqlalchemy import create_engine

engine = create_engine('mysql+pymysql://root:@127.0.0.1:3306/aaa')

Base = declarative_base()

class Son(Base):

    __tablename__ ='son'

    id = Column(Integer,primary_key=True)

    name = Column(String(32))

    age = Column(String(16))

    father_id = Column(Integer,ForeignKey('father.id'))

class Father(Base):

    __tablename__ = 'father'

    id = Column(Integer,primary_key=True)

    name = Column(String(32))

    age = Column(String(16))

    son = relationship('Son',backref='father')

# Base.metadata.create_all(engine)

Session = sessionmaker(bind=engine)

session = Session()

# f1 = session .query(Father).filter_by(id=1).first()

# w3 = Son(name='yiduiduo 333',age=11)

# f1.son.append(w3)

# s1 = session.query(Son).filter_by(di=2).first()

# print(s1.father.name)

# session.add_all([w3])

# session.commit()

# ret = session.query(Father.name,Son.name).join().all()

# print(ret)

# f1 =Father(name = 'alvin',age = 50)

#

# w1 = Son(name='yiduiduo 111',age=10)

# w2 = Son(name='yiduiduo 222',age=11)

# f1.son =[w1,w2]

#

# session.add_all([f1,w1,w2])

# session.commit()

实例 一对多

#!/usr/bin/env/python

# -*- coding:utf-8 -*-

from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy import Column,Integer,String,ForeignKey,UniqueConstraint,Index

from sqlalchemy.orm import  sessionmaker,relationship

from sqlalchemy import create_engine

engine = create_engine('mysql+pymysql://root:@127.0.0.1:3306/aaa?charset=utf8')  #建立连接

Base = declarative_base()  #创建ORM的基类

class Men_to_wemon(Base):  #创建关系映射表

    __tablename__ = 'men_to_wemon'   #定义数据表名

    nid = Column(Integer,primary_key=True)  #id 为整数类型 并且为主键

    men_id = Column(Integer,ForeignKey('men.id'))  #定义men_id 为整数类型，绑定Men类id

    women_id = Column(Integer,ForeignKey('women.id'))  #定义women_id 为整数类型，绑定women类id

class Men(Base):      #创建 男人表

    __tablename__ ='men'

    id = Column(Integer,primary_key=True)

    name = Column(String(32))

    age = Column(String(16))

    # gf = relationship('Women', secondary=Men_to_wemon.__table__)

class Women(Base):   #创建女人表

    __tablename__ ='women'

    id = Column(Integer,primary_key=True)

    name = Column(String(32))

    age = Column(String(16))

    bf = relationship('Men',secondary=Men_to_wemon.__table__,backref = 'gf') #定义关系映射 Men对应Men_to_wemon Women也对应Men_to_wemon

    # 一句话概括了两句对应关系，不需要再men表里继续定义关系了

Base.metadata.create_all(engine)

#通过激活sessionmaker 的__call__方法来return一个Session实例（Sesion类下提供了增删改查的具体方法）

Session = sessionmaker(bind=engine)

session = Session()

m1 =Men(name = 'alex',age=12)

m2 =Men(name = 'wusir',age = 12)

w1 = Women(name = '如哈',age = 20)

w2 = Women(name = '安安',age = 20)

session.add_all([m1,m2,w1,w2,])  #添加所有的数据

session.commit()

t1 = Men_to_wemon(men_id =1,women_id=2)

m1 = session.query(Men).filter_by(id =2).first()

w1 = session.query(Women).all()

m1.gf = w1

session.add_all([m1,])

session.commit()

实例 多对多

2、操作表

#!/usr/bin/env python

# -*- coding:utf-8 -*-

from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index

from sqlalchemy.orm import sessionmaker, relationship

from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5)

Base = declarative_base()

# 创建单表

class Users(Base):

    __tablename__ = 'users'

    id = Column(Integer, primary_key=True)

    name = Column(String(32))

    extra = Column(String(16))

    __table_args__ = (

    UniqueConstraint('id', 'name', name='uix_id_name'),

        Index('ix_id_name', 'name', 'extra'),

    )

    def __repr__(self):

        return "%s-%s" %(self.id, self.name)

# 一对多

class Favor(Base):

    __tablename__ = 'favor'

    nid = Column(Integer, primary_key=True)

    caption = Column(String(50), default='red', unique=True)

    def __repr__(self):

        return "%s-%s" %(self.nid, self.caption)

class Person(Base):

    __tablename__ = 'person'

    nid = Column(Integer, primary_key=True)

    name = Column(String(32), index=True, nullable=True)

    favor_id = Column(Integer, ForeignKey("favor.nid"))

    # 与生成表结构无关，仅用于查询方便

    favor = relationship("Favor", backref='pers')

# 多对多

class ServerToGroup(Base):

    __tablename__ = 'servertogroup'

    nid = Column(Integer, primary_key=True, autoincrement=True)

    server_id = Column(Integer, ForeignKey('server.id'))

    group_id = Column(Integer, ForeignKey('group.id'))

    group = relationship("Group", backref='s2g')

    server = relationship("Server", backref='s2g')

class Group(Base):

    __tablename__ = 'group'

    id = Column(Integer, primary_key=True)

    name = Column(String(64), unique=True, nullable=False)

    port = Column(Integer, default=22)

    # group = relationship('Group',secondary=ServerToGroup,backref='host_list')

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)

Session = sessionmaker(bind=engine)

session = Session()

表结构+ 数据连接

  • 增
obj = Users(name="alex0", extra='sb')

session.add(obj)

session.add_all([

    Users(name="alex1", extra='sb'),

    Users(name="alex2", extra='sb'),

])

session.commit()
  • 删
session.query(Users).filter(Users.id > 2).delete()

session.commit()
  • 改
session.query(Users).filter(Users.id > 2).update({"name" : ""})

session.query(Users).filter(Users.id > 2).update({Users.name: Users.name + ""}, synchronize_session=False)

session.query(Users).filter(Users.id > 2).update({"num": Users.num + 1}, synchronize_session="evaluate")

session.commit()
  • 查
ret = session.query(Users).all()

ret = session.query(Users.name, Users.extra).all()

ret = session.query(Users).filter_by(name='alex').all()

ret = session.query(Users).filter_by(name='alex').first()
  • 条件
#　条件

ret = session.query(Users).filter_by(name='alex').all()

ret = session.query(Users).filter(Users.id > 1, Users.name == 'eric').all()

ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all()

ret = session.query(Users).filter(Users.id.in_([1,3,4])).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='eric'))).all()

from sqlalchemy import and_, or_

ret = session.query(Users).filter(and_(Users.id > 3, Users.name == 'eric')).all()

ret = session.query(Users).filter(or_(Users.id < 2, 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('e%')).all()

ret = session.query(Users).filter(~Users.name.like('e%')).all()

# 限制

ret = session.query(Users)[1:2]

# 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 func

ret = session.query(Users).group_by(Users.extra).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

ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all()

ret = session.query(Person).join(Favor).all()

ret = session.query(Person).join(Favor, isouter=True).all()

# 组合

q1 = session.query(Users.name).filter(Users.id > 2)

q2 = session.query(Favor.caption).filter(Favor.nid < 2)

ret = q1.union(q2).all()

q1 = session.query(Users.name).filter(Users.id > 2)

q2 = session.query(Favor.caption).filter(Favor.nid < 2)

ret = q1.union_all(q2).all()

更多功能参见文档，猛击这里下载PDF

更多详情参考博文：http://www.cnblogs.com/wupeiqi/articles/5713330.html

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