用python连接mysql，实现一个银行转账的小功能

#coding=utf-8
import pymysql
import sys

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

    def check_acct_available(self, acctid):
        try:
            cursor = self.conn.cursor()
            sql = "select * from account where acctid=%s " % acctid
            cursor.execute(sql)
            print ("check_acct_available:" + 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):
        try:
            cursor = self.conn.cursor()
            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余额不足" % acctid)
        finally:
            cursor.close()

    def reduce_money(self, acctid, money):
        try:
            cursor = self.conn.cursor()
            sql = "update account set money= money-%s WHERE acctid=%s " % (money,acctid)
            cursor.execute(sql)
            print ("reduce_money:" + sql)
            rs = cursor.rowcount
            if rs != 1:
                raise Exception("账号%s付款失败" % acctid)
        finally:
            cursor.close()

    def add_money(self, acctid, money):
        try:
            cursor = self.conn.cursor()
            sql = "update account set money= money+%s WHERE acctid=%s " % (money,acctid)
            cursor.execute(sql)
            print("add_money:" + sql)
            rs = cursor.rowcount
            if rs != 1:
                raise Exception("账号%s收款失败" % 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()
            raise e
if __name__=="__main__":
    source_acctid = sys.argv[1]
    target_acctid = sys.argv[2]
    money = sys.argv[3]

    conn = pymysql.connect(
        host = '127.0.0.1',
        port = 3306,
        user = 'root',
        passwd = '1234',
        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()