python异常

                 

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)