Python *** 作 MySQL 的5种方式

1、MySQLdb

# 前置条件

sudo apt-get install python-dev libmysqlclient-dev # Ubuntu

sudo yum install python-devel mysql-devel # Red Hat / CentOS

# 安装

pip install MySQL-python

Windows 直接通过下载 exe 文件安装

#!/usr/bin/python

import MySQLdb

db = MySQLdb.connect(

host = "localhost", # 主机名

user = "root", # 用户名

passwd = "pythontab.com", # 密码

db = "testdb") # 数据库名称

# 查询前，必须先获取游标

cur = db.cursor()

# 执行的都是原生SQL语句

cur.execute("SELECT * FROM mytable")

for row in cur.fetchall():

print(row[0])

db.close()

2、mysqlclient

# Windows安装

pip install some-package.whl

# linux 前置条件

sudo apt-get install python3-dev # debian / Ubuntu

sudo yum install python3-devel # Red Hat / CentOS

brew install mysql-connector-c # macOS (Homebrew)

pip install mysqlclient

3、PyMySQL

pip install PyMySQL

# 为了兼容mysqldb，只需要加入

pymysql.install_as_MySQLdb()

import pymysql

conn = pymysql.connect(host = '127.0.0.1', user = 'root', passwd = "pythontab.com", db = 'testdb')

cur = conn.cursor()

cur.execute("SELECT Host,User FROM user")

for r in cur:

print(r)

cur.close()

conn.close()

4、peewee

pip install peewee

import peewee

from peewee import *

db = MySQLDatabase('testdb', user = 'root', passwd = 'pythontab.com')

class Book(peewee.Model):

author = peewee.CharField()

title = peewee.TextField()

class Meta:

database = db

Book.create_table()

book = Book(author = "pythontab", title = 'pythontab is good website')

book.save()

for book in Book.filter(author = "pythontab"):

print(book.title)

5、SQLAlchemy

from sqlalchemy import create_engine

from sqlalchemy.orm import sessionmaker

from sqlalchemy_declarative import Address, Base, Person

class Address(Base):

__tablename__ = 'address'

id = Column(Integer, primary_key = True)

street_name = Column(String(250))

engine = create_engine('sqlite:///sqlalchemy_example.db')

Base.metadata.bind = engine

DBSession = sessionmaker(bind = engine)

session = DBSession()

# Insert a Person in the person table

new_person = Person(name = 'new person')

session.add(new_person)

session.commit()

以 Debian/Ubuntu 为例（请确保有管理员权限）：

1.MySQL

代码如下:

apt-get install mysql-server

apt-get install mysql-client

apt-get install libmysqlclient15-dev

2.python-mysqldb

代码如下:

apt-get install python-mysqldb

3.easy_install

代码如下:

wget http://peak.telecommunity.com/dist/ez_setup.py

python ez_setup.py

4.MySQL-Python

代码如下:

easy_install MySQL-Python

5.SQLAlchemy

代码如下:

easy_install SQLAlchemy

6、安装完成后使用下面代码测试连接

代码如下：

from sqlalchemy import create_engine

from sqlalchemy.orm import sessionmaker

DB_CONNECT_STRING = 'mysql+mysqldb://root:123@localhost/ooxx?charset=utf8'

engine = create_engine(DB_CONNECT_STRING, echo=True)

DB_Session = sessionmaker(bind=engine)

session = DB_Session()

7、数据 *** 作（增删改查）

代码如下：

from sqlalchemy import func, or_, not_

user = User(name='a')

session.add(user)

user = User(name='b')

session.add(user)

user = User(name='a')

session.add(user)

user = User()

session.add(user)

session.commit()

query = session.query(User)

print query # 显示SQL 语句

print query.statement # 同上

for user in query: # 遍历时查询

print user.name

print query.all() # 返回的是一个类似列表的对象

print query.first().name # 记录不存在时，first() 会返回 None

# print query.one().name # 不存在，或有多行记录时会抛出异常

print query.filter(User.id == 2).first().name

print query.get(2).name # 以主键获取，等效于上句

print query.filter('id = 2').first().name # 支持字符串

query2 = session.query(User.name)

print query2.all() # 每行是个元组

print query2.limit(1).all() # 最多返回 1 条记录

print query2.offset(1).all() # 从第 2 条记录开始返回

print query2.order_by(User.name).all()

print query2.order_by('name').all()

print query2.order_by(User.name.desc()).all()

print query2.order_by('name desc').all()

print session.query(User.id).order_by(User.name.desc(), User.id).all()

print query2.filter(User.id == 1).scalar() # 如果有记录，返回第一条记录的第一个元素

print session.query('id').select_from(User).filter('id = 1').scalar()

print query2.filter(User.id >1, User.name != 'a').scalar() # and

query3 = query2.filter(User.id >1) # 多次拼接的 filter 也是 and

query3 = query3.filter(User.name != 'a')

print query3.scalar()

print query2.filter(or_(User.id == 1, User.id == 2)).all() # or

print query2.filter(User.id.in_((1, 2))).all() # in

query4 = session.query(User.id)

print query4.filter(User.name == None).scalar()

print query4.filter('name is null').scalar()

print query4.filter(not_(User.name == None)).all() # not

print query4.filter(User.name != None).all()

print query4.count()

print session.query(func.count('*')).select_from(User).scalar()

print session.query(func.count('1')).select_from(User).scalar()

print session.query(func.count(User.id)).scalar()

print session.query(func.count('*')).filter(User.id >0).scalar() # filter() 中包含 User，因此不需要指定表

print session.query(func.count('*')).filter(User.name == 'a').limit(1).scalar() == 1 # 可以用 limit() 限制 count() 的返回数

print session.query(func.sum(User.id)).scalar()

print session.query(func.now()).scalar() # func 后可以跟任意函数名，只要该数据库支持

print session.query(func.current_timestamp()).scalar()

print session.query(func.md5(User.name)).filter(User.id == 1).scalar()

query.filter(User.id == 1).update({User.name: 'c'})

user = query.get(1)

print user.name

user.name = 'd'

session.flush() # 写数据库，但并不提交

print query.get(1).name

session.delete(user)

session.flush()

print query.get(1)

session.rollback()

print query.get(1).name

query.filter(User.id == 1).delete()

session.commit()

print query.get(1)

map是把函数调用的结果放在列表里面返回，它也可以接受多个 iterable,在第n次调用function时，将使用iterable1[n], iterable2[n], ...作为参数。

filter(function, iterable)

这个函数的功能是过滤出iterable中所有以元素自身作为参数调用function时返回True或bool(返回值)为True的元素并以列表返回.

def f_large_than_5(x):

return x >5

filter(f_large_than_5, range(10))

>>[6,7,8,9]

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