python知识-python操作MySQL数据库
python DB API
python访问数据库的统一接口规范
DB API-连接数据库对象connection
创建方法：MySQLdb.Connect(参数)
connection对象支持的方法
DB API-数据库游标对象cursor
游标对象：用于执行查询和获取结果
cursor支持的方法：
execute方法：执行SQL，近结果从数据库返回到客户端
案例：
创建一个user表
create table user(
userid int(11) not null auto_increment,
username varchar(100) default null,
primary key (userid)
)engine=innodb auto_increment=9 default charset=utf8;
插入数据：
insert into user values ('','name1'),('','name2'),('','name3'),('','name4'),('','name5'),('','name6'),('','name7'),('','name8'),('','name9');
代码：
import MySQLdb
conn = MySQLdb.connect(host = '127.0.0.1',port = 3306,user = 'root',passwd = '',db = 'imooc',charset='utf8')
cursor = conn.cursor()
sql="select * from user"
cursor.execute(sql)
rs=cursor.fetchall()
for row in rs:
print "userid=%s,username=%s" % row
cursor.close()
conn.close()
结果是：
userid=9,username=name1
userid=10,username=name2
userid=11,username=name3
userid=12,username=name4
userid=13,username=name5
userid=14,username=name6
userid=15,username=name7
userid=16,username=name8
userid=17,username=name9
实例演示：insert/update/delete更新数据库
import MySQLdb
conn = MySQLdb.connect(host = '127.0.0.1',port = 3306,user = 'root',passwd = '',db = 'imooc',charset='utf8')
cursor = conn.cursor()
sql_insert="insert into user (userid,username) values ('','name10')"
sql_update="update user set username='name91' where userid=9"
sql_delete="delete from user where userid=13"
try:
cursor.execute(sql_insert)
print cursor.rowcount
cursor.execute(sql_update)
print cursor.rowcount
cursor.execute(sql_delete)
print cursor.rowcount
conn.commit()
except Exception as e:
print e
conn.rollback()
cursor.close()
conn.close()
实例：银行转账系统
创建表：
create table account(
acctid int(11) default null,
money int(11) default null
)engine=innodb default charset=utf8;
说明：数据库的引擎这边不能设置为MyISAM，因为它支持事物
插入数据：
insert into account values (11,110),(12,10);
代码：
# -*- coding: utf-8 -*-
"""
Created on Wed Jan 06 10:09:09 2016
@author: lenovo
"""
import sys
import MySQLdb
class TransferMoney(object):
def __init__(self,conn):
self.conn=conn
def check_acct_avaiable(self,acctid):
cursor=self.conn.cursor()
try:
sql="select * from account where acctid=%s" % acctid
cursor.execute(sql)
print "check_acct_avaiable:"+sql
rs=cursor.fetchall()
if len(rs)!=1:
raise Exception("账号%s不存在" % acctid)
finally:
cursor.close()
def has_enough_money(self,acctid,money):
cursor=self.conn.cursor()
try:
sql="select * from account where acctid=%s and money>%s" % (acctid,money)
cursor.execute(sql)
print "has_enough_money:"+sql
rs=cursor.fetchall()
if len(rs)!=1:
raise Exception("账号%s没有足够的钱" % acctid)
finally:
cursor.close()
def reduce_money(self,acctid,money):
cursor=self.conn.cursor()
try:
sql="update account set money=money-%s where acctid=%s" % (money,acctid)
cursor.execute(sql)
print "reduce_money:"+sql
if cursor.rowcount != 1:
raise Exception("账号%s减款失败" % acctid)
finally:
cursor.close()
def add_money(self,acctid,money):
cursor=self.conn.cursor()
try:
sql="update account set money=money+%s where acctid=%s" % (money,acctid)
cursor.execute(sql)
print "add_money:"+sql
if cursor.rowcount != 1:
raise Exception("账号%s加款失败" % acctid)
finally:
cursor.close()
def transfer(self,source_acctid,target_acctid,money):
try:
self.check_acct_avaiable(source_acctid)
self.check_acct_avaiable(target_acctid)
self.has_enough_money(source_acctid,money)
self.reduce_money(source_acctid,money)
self.add_money(target_acctid,money)
self.conn.commit()
except Exception as e:
self.conn.rollback()
raise e
if __name__=="__main__":
source_acctid=sys.argv[1]
target_acctid=sys.argv[2]
money=sys.argv[3]
conn = MySQLdb.connect(host = '127.0.0.1',port = 3306,user = 'root',passwd = '',db = 'imooc',charset='utf8')
tr_money=TransferMoney(conn)
try:
tr_money.transfer(source_acctid,target_acctid,money)
except Exception as e:
print "出现问题："+str(e)
finally:
conn.close()