Python初学者:如何防止“finally”执行?

# Connect to the DB
try:
    dbi = MySQLdb.connect(host='localhost', \
                          user='user', \
                          passwd='pass', \
                          db='dbname', \
                          port=3309)

    print "Connected to DB ..."

except MySQLdb.Error, e:
    apiErr = 2
    apiErrMsg = "Error %d: %s" % (e.args[0], e.args[1])
    return

    # To prevent try..finally bug in python2.4,
    # one has to nest the "try: except:" part. 
try:
    try:
        sql = dbi.cursor()
        sql.execute("""
        SELECT *
        FROM table
        WHERE idClient =  %s
        """, (key, ))

        access = sql.fetchall()

        # [some more code here]           

    except MySQLdb.Error, e:
        apiErr = 2
        apiErrMsg = "Error %d: %s" % (e.args[0], e.args[1])
        return

finally:
    sql.close()
    dbi.close()

(注意:使用python 2.4)

澄清:我不知道MySQLdb在发生错误时是否会自动关闭连接。我在上面的代码中遇到的问题是,当建立连接时出错(代码的第一个try块),在finally块中调用dbi.close()会引发“AttributeError:'NoneType'对象没有dbi的属性'close'”。..

:

# define at the start 
dbi = None
sql = None

在最后一块中,

if sql is not None:
    sql.close()
if dbi is not None:
    dbi.close()