python下异常处理

1、python下异常如何处理：

 #encoding=utf-8

 """
 python遇到异常，程序直接运行
 try:
     "判断有可能抛出异常的代码"
     print "haha"
 except:
     "异常下运行的代码"
 else:
     "运行没有异常时候的逻辑"
 finally:
     "不管try判断如何，该代码总会执行"

 合理利用异常：
     1、不得不用的地方采用异常;
     2、正确使用异常：需要对异常进行捕获
      比如：except IOError:   

 """

 a = [1, 2, 3, 4, 5, 6]

 print a[4]

 try:
     print a[6]
 except:
     print u'哈哈'

 print "继续可以到这里"

 try:
     print a[6]
 except:
     print "huhu"
 else:
     print "hoho"
 finally:
     print "hehe"

 import urllib
 sth_url = "http://wsdfsdf"

 try:
     d = urllib.urlopen(sth_url)
 except:
     print "出错了"
 else:
     content = d.read()
 finally:
     pass
     #d.close()

 """
 异常的note：
     1、一个try对应一个except
     2、使用python内置异常，来对应自身情况；
     IOErro, IndexError
     3、捕获异常的办法：
         import logging
         logger = logging.getLogger()
         #logfile = 'excetion_demo.log'    #log文件名
         hdlr = logging.FileHandler('/tmp/sendlog.txt')
         formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')
         hdlr.setFormatter(formatter)
         logger.addHandler(hdlr)  #logging绑定
         logger.setLevel(logging.NOTSET)

         import sys, logging
         try:
             d = urllib.urlopen("www.kdkdk.com")
         except:
             exc = sys.exc_info()
             loggin.debug(exc[1]
             print exc[1]
             print exc
     4、断言，assert
         assert 表达式，"出错后抛出message"
         assert 1>4,  "expression Error"
     先断言绝对不能发生的错误，然后在处理异常；
 """

 """
 with用法：自动回收垃圾
 #进入时，调用对象的__enter__
 #退出时，调用对象的__exit__函数

 d = open('a', 'r')
 d.read()
 d.close()

 with open('a', 'r')  as d:
     content = a.read()
 """

 #with示例：
 class sth(object):
     def __init__(self, xixi):
         self.a  = xixi

     def __enter__(self):
         print u'哈哈， 进来了'
         return self.a

     def __exit__(self, type, value, traceback):
         print u'哈哈，出去了'

 with sth("gg") as s:
     print s         #s为__enter__返回值

 """
 定义自己的异常类
 """

 class myException(Exception):
     def __init__(self, error, msg):
         self.args = (error, msg)
         self.error = error
         self.msg  = msg

 try:
     raise myException(1, "my exception")
 except Exception as e:
     print str(e)