python下异常如何处理：
1 #encoding=utf-8
2
3 """
4 python遇到异常，程序直接运行
5 try:
6 "判断有可能抛出异常的代码"
7 print "haha"
8 except:
9 "异常下运行的代码"
10 else:
11 "运行没有异常时候的逻辑"
12 finally:
13 "不管try判断如何，该代码总会执行"
14
15 合理利用异常：
16 1、不得不用的地方采用异常;
17 2、正确使用异常：需要对异常进行捕获
18 比如：except IOError:
19
20 """
21
22 a = [1, 2, 3, 4, 5, 6]
23
24 print a[4]
25
26 try:
27 print a[6]
28 except:
29 print u'哈哈'
30
31 print "继续可以到这里"
32
33
34 try:
35 print a[6]
36 except:
37 print "huhu"
38 else:
39 print "hoho"
40 finally:
41 print "hehe"
42
43
44 import urllib
45 sth_url = "http://wsdfsdf"
46
47 try:
48 d = urllib.urlopen(sth_url)
49 except:
50 print "出错了"
51 else:
52 content = d.read()
53 finally:
54 pass
55 #d.close()
56
57 """
58 异常的note：
59 1、一个try对应一个except
60 2、使用python内置异常，来对应自身情况；
61 IOErro, IndexError
62 3、捕获异常的办法：
63 import logging
64 logger = logging.getLogger()
65 #logfile = 'excetion_demo.log' #log文件名
66 hdlr = logging.FileHandler('/tmp/sendlog.txt')
67 formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')
68 hdlr.setFormatter(formatter)
69 logger.addHandler(hdlr) #logging绑定
70 logger.setLevel(logging.NOTSET)
71
72
73 import sys, logging
74 try:
75 d = urllib.urlopen("www.kdkdk.com")
76 except:
77 exc = sys.exc_info()
78 loggin.debug(exc[1]
79 print exc[1]
80 print exc
81 4、断言，assert
82 assert 表达式，"出错后抛出message"
83 assert 1>4, "expression Error"
84 先断言绝对不能发生的错误，然后在处理异常；
85 """
86
87 """
88 with用法：自动回收垃圾
89 #进入时，调用对象的__enter__
90 #退出时，调用对象的__exit__函数
91
92 d = open('a', 'r')
93 d.read()
94 d.close()
95
96 with open('a', 'r') as d:
97 content = a.read()
98 """
99
100 #with示例：
101 class sth(object):
102 def __init__(self, xixi):
103 self.a = xixi
104
105 def __enter__(self):
106 print u'哈哈， 进来了'
107 return self.a
108
109 def __exit__(self, type, value, traceback):
110 print u'哈哈，出去了'
111
112 with sth("gg") as s:
113 print s #s为__enter__返回值
114
115 """
116 定义自己的异常类
117 """
118
119 class myException(Exception):
120 def __init__(self, error, msg):
121 self.args = (error, msg)
122 self.error = error
123 self.msg = msg
124
125 try:
126 raise myException(1, "my exception")
127 except Exception as e:
128 print str(e)
