mysql for python,银行转账模拟

学习中， 本人为初学者。勿喷。

#-*- coding:utf-8 -*-
import MySQLdb
class Tranferaccount(object):
    def __init__(self,sqlcon):
        self.sqlcon = sqlcon
    def account_check_avaiable(self,accid):
        cursor = self.sqlcon.cursor()
        sql_str = "select * from account where accid = %s "% accid
        try:
            print 'account_check_avaiable:%s'%sql_str
            cursor.execute(sql_str)
            rs = cursor.fetchall()
            if len(rs)!=1:
                raise Exception('此账号%s不存在'%accid) 
        finally:
            cursor.close()
    def account_enough_money(self,accid,money):
        cursor = self.sqlcon.cursor()
        sql_str = "select * from account where accid = %s and money >%s "% (accid,money)
        try:
            print 'account_enough_money:%s'%sql_str
            cursor.execute(sql_str)
            rs = cursor.fetchall()
            if len(rs)!=1:
                raise Exception('此账号%s余额不足'%accid)
        finally:
            cursor.close()
    def account_reduce_money(self,accid,money):
        cursor = self.sqlcon.cursor()
        sql_str = "update account set money = money-%s where accid = %s "% (money,accid)
        try:
            print 'account_reduce_money:%s'%sql_str
            cursor.execute(sql_str)
            if cursor.rowcount != 1:
                raise Exception('此账号%s减款失败'%accidd)
        finally:
            cursor.close()
    def account_add_money(self,accid,money):
        cursor = self.sqlcon.cursor()
        sql_str = "update account set money = money+%s where accid = %s "% (money,accid)
        try:
            print 'account_add_money:%s'%sql_str
            cursor.execute(sql_str)
            if cursor.rowcount != 1:
                raise Exception('此账号%s加款失败'%accid)
        finally:
            cursor.close()                                        
    def tranfer(self,source_accid,dest_accid,money):
        try:
            self.account_check_avaiable(source_accid)
            self.account_check_avaiable(dest_accid)
            self.account_enough_money(source_accid,money)
            self.account_reduce_money(source_accid,money)
            self.account_add_money(dest_accid,money)
            self.sqlcon.commit()
        except Exception as e:
            self.sqlcon.rollback()
            raise e
if __name__ == "__main__":
    source_accid = 11
    dest_accid = 12
    money = 100
    conn = MySQLdb.connect(host='127.0.0.1',user='root',db = 'liunx',passwd='root',port=3306,charset='utf8')
    tr_money = Tranferaccount(conn)
    try:
        tr_money.tranfer(source_accid,dest_accid,money)
    except Exception as e:
        print '出现问题:%s'% e
    finally:  
        conn.close()