Python3连接MySQL（pymysql）模拟转账实现代码

# coding:utf8import sysimport 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      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):    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余额不足"% 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_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 = 'localhost',            unix_socket = "..mysql/mysql.sock",            port = 3306,            user = 'root',            passwd = '',            db = 'python_db',                    )  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()