异常

查看异常类

import exceptions
dir(exceptions)

引发异常

raise Exception
raise Exception("Oh, some problem")

捕获异常

except捕获异常

try:
    x = input()
    y = input()
    print x/y
except ZeroDivisionError:
    print "the 2nd number can not be 0"

在except中不指定异常类，所有异常都会被捕获

try:
    x = input()
    y = input()
    print x/y
except :
    print "the 2nd number can not be 0"

跟前一个的区别是，前一个只捕获除０异常，后者还可以捕获类型错误等等．

给except提供两个参数

打印异常信息：

try:
    ...　
except Exception, e:
    ...

访问异常对象本身

try:
    x = input()
    y = input()
    print x/y
except （ZeroDivisionError，　typeError), e:
# 在３．０版本中　　except （ZeroDivisionError，　typeError)　as e:
    print e

重新引发异常

#!/usr/bin/env python
class MuffledCalculator:
	muffled = False
	def calc(self, expr):
		try:
			return eval(expr)
		except ZeroDivisionError:
			if self.muffled:
				print 'Division by zero is illegal!'　　＃　异常处理到此终止
			else:
				raise  # 异常传递


calculator = MuffledCalculator()
print calculator.calc('10/2')

print calculator.calc('10/0')
self.muffled = True
print calculator.calc('10/0')

else子句，没有引发异常，执行该子句

while True:
    try:
        x = input()
        y = input()
        print x/y
    except Exception,e:
        print e
        print "try again"
    else:
        break

finally子句：关闭文件或者网络套接字