1.Python内建异常体系结构
The class hierarchy for built-in exceptions is:
BaseException
+-- SystemExit
+-- KeyboardInterrupt
+-- GeneratorExit
+-- Exception
+-- StopIteration
+-- StandardError
| +-- BufferError
| +-- ArithmeticError
| | +-- FloatingPointError
| | +-- OverflowError
| | +-- ZeroDivisionError
| +-- AssertionError
| +-- AttributeError
| +-- EnvironmentError
| | +-- IOError
| | +-- OSError
| | +-- WindowsError (Windows)
| | +-- VMSError (VMS)
| +-- EOFError
| +-- ImportError
| +-- LookupError
| | +-- IndexError
| | +-- KeyError
| +-- MemoryError
| +-- NameError
| | +-- UnboundLocalError
| +-- ReferenceError
| +-- RuntimeError
| | +-- NotImplementedError
| +-- SyntaxError
| | +-- IndentationError
| | +-- TabError
| +-- SystemError
| +-- TypeError
| +-- ValueError
| +-- UnicodeError
| +-- UnicodeDecodeError
| +-- UnicodeEncodeError
| +-- UnicodeTranslateError
+-- Warning
+-- DeprecationWarning
+-- PendingDeprecationWarning
+-- RuntimeWarning
+-- SyntaxWarning
+-- UserWarning
+-- FutureWarning
+-- ImportWarning
+-- UnicodeWarning
+-- BytesWarning
2.捕获异常的方式
方法一：捕获所有的异常
''' 捕获异常的第一种方式，捕获所有的异常 '''
try:
a = b
b = c
except Exception,data:
print Exception,":",data
'''输出：<type 'exceptions.Exception'> : local variable 'b' referenced before assignment ''
--------------------------------------------------------------------------------
方法二：采用traceback模块查看异常，需要导入traceback模块
''' 捕获异常的第二种方式，使用traceback查看异常 '''
try:
a = b
b = c
except:
print traceback.print_exc()
'''输出： Traceback (most recent call last):
File "test.py", line 20, in main
a = b
UnboundLocalError: local variable 'b' referenced before assignmen
--------------------------------------------------------------------------------
方法三：采用sys模块回溯最后的异常
''' 捕获异常的第三种方式，使用sys模块捕获异常 '''
try:
a = b
b = c
except:
info = sys.exc_info()
print info
print info[0]
print info[1]
'''输出：
(<type 'exceptions.UnboundLocalError'>, UnboundLocalError("local variable 'b' referenced before assignment",),
<traceback object at 0x00D243F0>)
<type 'exceptions.UnboundLocalError'>
local variable 'b' referenced before assignment
'''
-------------------------------------------------------------------------------
1、NameError：尝试访问一个未申明的变量
>>> v
NameError: name 'v' is not defined
2、ZeroDivisionError：除数为0
>>> v = 1/0
ZeroDivisionError: int division or modulo by zero
3、SyntaxError：语法错误
>>> int int
SyntaxError: invalid syntax (<pyshell#14>, line 1)
4、IndexError：索引超出范围
>>> List = [2]
>>> List[3]
Traceback (most recent call last):
File "<pyshell#18>", line 1, in <module>
List[3]
IndexError: list index out of range
5、KeyError：字典关键字不存在
>>> Dic = {'1':'yes', '2':'no'}
>>> Dic['3']
Traceback (most recent call last):
File "<pyshell#20>", line 1, in <module>
Dic['3']
KeyError: '3'
6、IOError：输入输出错误
>>> f = open('abc')
IOError: [Errno 2] No such file or directory: 'abc'
7、AttributeError：访问未知对象属性
>>> class Worker:
def Work():
print("I am working")
>>> w = Worker()
>>> w.a
Traceback (most recent call last):
File "<pyshell#51>", line 1, in <module>
w.a
AttributeError: 'Worker' object has no attribute 'a'
8、ValueError：数值错误
>>> int('d')
Traceback (most recent call last):
File "<pyshell#54>", line 1, in <module>
int('d')
ValueError: invalid literal for int() with base 10: 'd'
9、TypeError：类型错误
>>> iStr = '22'
>>> iVal = 22
>>> obj = iStr + iVal;
Traceback (most recent call last):
File "<pyshell#68>", line 1, in <module>
obj = iStr + iVal;
TypeError: Can't convert 'int' object to str implicitly
10、AssertionError：断言错误
>>> assert 1 != 1
Traceback (most recent call last):
File "<pyshell#70>", line 1, in <module>
assert 1 != 1
AssertionError
11、MemoryError:内存耗尽异常
12、NotImplementedError：方法没实现引起的异常
示例：
1 class Base(object): 2 def __init__(self): 3 pass 4 5 def action(self): 6 raise NotImplementedError
定义一个类，一个接口方法action,如果直接调用action则抛NotImplementedError异常，这样做的目的通常是用来模拟接口
13、LookupError：键、值不存在引发的异常
LookupError异常是IndexError、KeyError的基类
如果你不确定数据类型是字典还是列表时，可以用LookupError捕获此异常
14、StandardError 标准异常。
除StopIteration, GeneratorExit, KeyboardInterrupt 和SystemExit外，其他异常都是StandarError的子类。
异常处理有别于错误检测：
错误检测与异常处理区别在于：错误检测是在正常的程序流中，处理不可预见问题的代码，例如一个调用操作未能成功结束
