Python学习系列（七）( 数据库编程）

Python学习系列（七）( 数据库编程）

       Python学习系列（六）(模块)

一，MySQL-Python插件

      Python里操作MySQL数据库，需要Python下安装访问MySQL数据库接口API包即插件，从而使得Python2.7能访问操作MySQL数据库。MySQL软件可以去官网下载：http://www.mysql.com/; MySQLdb插件下载：http://sourceforge.net/projects/mysql-python/files/latest/download

二，访问MySQL数据库

    1，连接数据库mysql

         基本格式：connect ([host=]'ip',[user=]'user',[passwd=]'password',[db=]'dbname')

    2，数据库的基本操作

     1）create创建表

 import MySQLdb
 #connect to a database 'test'
 conn=MySQLdb.connect(host='localhost',user='root',passwd='zbc123',db='test')
 cursor=conn.cursor()
 #create a table
 cursor.execute('create table \
 test(ID int primary key auto_increment,Name char(25))')
 #Closing database
 cursor.close()
 conn.close()

     2）fetchall访问：

 import MySQLdb
 #connect to a database 'test'
 conn=MySQLdb.connect(host='localhost',user='root',passwd='zbc123',db='test')
 cursor=conn.cursor()
 #fetch datas
 n=cursor.execute('select * from test;')
 r=cursor.fetchall()
 print n,r
 #Closing database
 cursor.close()
 conn.close()

 >>> ================================ RESTART ================================
 >>>
 3 ((4L, 'zhangbc'), (5L, 'lis08'), (6L, 'wangw'))
 >>> 

 

在Mysql5.6环境下运行：

3）insert向表中插入数据：

 import MySQLdb
 #connect to a database 'test'
 conn=MySQLdb.connect(host='localhost',user='root',passwd='zbc123',db='test')
 cursor=conn.cursor()
 #insert data into table 'test'
 mysql='''insert into test(id,sname) values(4,'zhanghua')'''
 cursor.execute(mysql)
 conn.commit()#below mysql5.0 needed
 #fetch datas
 n=cursor.execute('select * from test;')
 r=cursor.fetchall()
 print n,r
 #Closing database
 cursor.close()
 conn.close()

 >>> ================================ RESTART ================================
 >>>
 4 ((1L, 'zhangbc'), (2L, 'lis'), (3L, 'wangw'), (4L, 'zhanghua'))

注意：一定要写上conn.commit();事物不提交，将回滚。比较：

 

4）update修改表中数据：

 import MySQLdb
 #connect to a database 'test'
 conn=MySQLdb.connect(host='localhost',user='root',passwd='zbc123',db='test')
 cursor=conn.cursor()
 #update data of the table 'test'
 mysql='''update test set sname='Lisi08' where id=2'''
 cursor.execute(mysql)
 conn.commit()#below mysql5.0 needed
 #fetch datas
 n=cursor.execute('select * from test;')
 r=cursor.fetchall()
 print n,r
 #Closing database
 cursor.close()
 conn.close()

 >>> ================================ RESTART ================================
 >>>
 4 ((1L, 'zhangbc'), (2L, 'Lisi08'), (3L, 'wangw'), (4L, 'zhanghua'))

5）delete删除表中数据：

 import MySQLdb
 #connect to a database 'test'
 conn=MySQLdb.connect(host='localhost',user='root',passwd='zbc123',db='test')
 cursor=conn.cursor()
 #delete data of the table 'test'
 mysql='''delete from test where id=4'''
 cursor.execute(mysql)
 conn.commit()#below mysql5.0 needed
 #fetch datas
 n=cursor.execute('select * from test;')
 r=cursor.fetchall()
 print n,r
 #Closing database
 cursor.close()
 conn.close()

 >>> ================================ RESTART ================================
 >>>
 3 ((1L, 'zhangbc'), (2L, 'Lisi08'), (3L, 'wangw'))

     6）关于select及其遍历：

      i）使用元组tuple与fetchone结合

 import MySQLdb
 #connect to a database 'test'
 conn=MySQLdb.connect(host='localhost',user='root',passwd='zbc123',db='test')
 cursor=conn.cursor()
 #fetch datas
 cursor.execute('select * from test;')
 #获得结果集的记录
 numrows=int(cursor.rowcount)
 #循环，取行数据
 for i in range(numrows):
     row=cursor.fetchone()
     print row[0],row[1]
 #Closing database
 cursor.close()
 conn.close()

 >>> ================================ RESTART ================================
 >>>
 4 zhangbc
 5 lis08
 6 wangw

ii）使用字典cursor

 #-*- coding:UTF-8 -*-
 import MySQLdb as mdb
 #connect to a database 'test'
 conn=mdb.connect(host='localhost',user='root',passwd='zbc123',db='test')
 with conn:
     #获取连接上的字典cursor，每一个cursor其实都是cursor的子类
     cur=conn.cursor(mdb.cursors.DictCursor)
 #fetch datas
 cur.execute('select * from test;')
 #获得结果集
 rows=cur.fetchall()
 #循环，取行数据
 for row in rows:
     print '%s %s'%(row['ID'],row['Name'])
 #Closing database
 cur.close()
 conn.close()

 >>> ================================ RESTART ================================
 >>>
 4 zhangbc
 5 lis08
 6 wangw

iii）获取单个表的字段名及其信息

 #-*- coding:UTF-8 -*-
 import MySQLdb as mdb
 #connect to a database 'test'
 conn=mdb.connect(host='localhost',user='root',passwd='zbc123',db='test')
 with conn:
     #获取连接上的字典cursor，每一个cursor其实都是cursor的子类
     cur=conn.cursor()
 #fetch datas
 cur.execute('select * from test;')
 #获得结果集
 rows=cur.fetchall()
 #获得链接对象的描述信息
 desc=cur.description
 print 'cur.description:',desc
 #打印表头
 print '%2s %3s'%(desc[0][0],desc[1][0])
 #循环，取行数据
 for row in rows:
     print '%2s %3s'%row
 #Closing database
 cur.close()
 conn.close()

 >>> ================================ RESTART ================================
 >>>
 cur.description: (('ID', 3, 1, 11, 11, 0, 0), ('Name', 254, 7, 25, 25, 0, 1))
 ID Name
  4 zhangbc
  5 lis08
  6 wangw

三，小结

     本文主要介绍了Python下如何访问并操数据库的基本知识，如：如何连接数据库，如何执行执行SQL语句等等。