python，mysql简易的原子操作

利用mysql的LAST_INSERT_ID实现一个简单的自增长的id。
mysql建表

CREATE TABLE `sequence` (
    `id` int NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
#初始化
INSERT INTO sequence VALUES (0);

#-*- coding: utf8 -*-
import MySQLdb
import settings

def generate():
    db_args = settings.DB_ACCOUNT_PASSWORD['farm']
    db = MySQLdb.connect(host=db_args[2], user=db_args[0], passwd=db_args[1], 
                         db=db_args[3])
    db.autocommit(True)
    
    cursor = db.cursor()
    
    try:
        cursor.execute("UPDATE sequence SET id=LAST_INSERT_ID(id+1)")
        cursor.execute("SELECT LAST_INSERT_ID()")
        
        uid = str(int(cursor.fetchone()[0]))
        
    except MySQLdb.Error, e:
        print 'mysql err'
        return None
    finally:
        cursor.close()
    
    return uid