Python3连接MySQL（pymysql）模拟转账实现代码

# 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
      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()