Python学习笔记 - MySql的使用

一、安装MySql模块

Python2.X

pip install MySQLdb

Python3.X

pip install pymysql

二、数据库连接接口

由于Python统一了数据库连接的接口，所以 pymysql 和 MySQLdb 在使用方式上是类似的：

pymysql.Connect()参数说明
host(str):      MySQL服务器地址
port(int):      MySQL服务器端口号
user(str):      用户名
passwd(str):    密码
db(str):        数据库名称
charset(str):   连接编码

connection对象支持的方法
cursor()        使用该连接创建并返回游标
commit()        提交当前事务
rollback()      回滚当前事务
close()         关闭连接

cursor对象支持的方法
execute(op)     执行一个数据库的查询命令
fetchone()      取得结果集的下一行
fetchmany(size) 获取结果集的下几行
fetchall()      获取结果集中的所有行
rowcount()      返回数据条数或影响行数
close()         关闭游标对象

三、范例

MySql脚本

-- ----------------------------
-- Table structure for account
-- ----------------------------
DROP TABLE IF EXISTS `account`;
CREATE TABLE `account`  (
  `acctid` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `name` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `money` decimal(50, 0) NULL DEFAULT NULL
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of account
-- ----------------------------
INSERT INTO `account` VALUES ('', '张三', 50);
INSERT INTO `account` VALUES ('', '李四', 150);

Python程序

#   coding:utf8
import sys
import pymysql

class TransferMoney(object):
    def __init__(self, conn):
        self.conn = conn

    def check_acct_available(self, acctid):
        cursor = self.conn.cursor()
        try:
            sql = "select * from account where acctid='%s'" % acctid
            print("check_acct_available:" + sql)
            cursor.execute(sql)
            rs = cursor.fetchall()
            if len(rs) != 1:
                raise Exception("帐号%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)
            print("has_enough_money:" + sql)
            cursor.execute(sql)
            rs = cursor.fetchall()
            if len(rs) != 1:
                raise Exception("帐号%s没有足够的金额" % 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)
            print("reduce_money:" + sql)
            cursor.execute(sql)
            if cursor.rowcount != 1:
                raise Exception("帐号%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)
            print("add_money:" + sql)
            cursor.execute(sql)
            if cursor.rowcount != 1:
                raise Exception("帐号%s加款失败" % acctid)
        finally:
            cursor.close()

    def transfer(self, source_acctid, target_acctid, money):
        try:
            self.check_acct_available(source_acctid)
            self.check_acct_available(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()
            print("transfer出现异常：" + str(e))
            raise e

def main():
    source_acctid = sys.argv[1]
    print("转出帐号=" + source_acctid)
    target_acctid = sys.argv[2]
    print("转入帐号=" + target_acctid)
    money = sys.argv[3]
    print("金额=" + money)

    # 连接数据库
    conn = pymysql.Connect(
        host='localhost',
        port=3306,
        user='root',
        passwd='root',
        db='OtkDb',
        charset='utf8')

    tr_money = TransferMoney(conn)

    try:
        tr_money.transfer(source_acctid, target_acctid, money)
    except Exception as e:
        print("main出现异常：" + str(e))
    finally:
        conn.close()

if __name__ == '__main__':
    main()

四、运行效果

PS H:\web\Python> & python h:\web\Python\01.MySql\db.py 1 2 50
转出帐号=1
转入帐号=2
金额=50
check_acct_available:select * from account where acctid='1'
check_acct_available:select * from account where acctid='2'
has_enough_money:select * from account where acctid='1' and money>50
reduce_money:update account set money=money-50 where acctid='1'
add_money:update account set money=money+50 where acctid='2'

PS H:\web\Python> & python h:\web\Python\01.MySql\db.py 1 2 50
转出帐号=1
转入帐号=2
金额=50
check_acct_available:select * from account where acctid='1'
check_acct_available:select * from account where acctid='2'
has_enough_money:select * from account where acctid='1' and money>50
transfer出现异常：帐号1没有足够的金额
main出现异常：帐号1没有足够的金额

参考：

http://www.cnblogs.com/woider/p/5926744.html