pyMysql

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

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