python exception

python exception的實例參考

一、捕獲固定異常

# -*- coding: utf-8 -*-

while True:
	try:
		x = int(raw_input("please input a number:"))
		print x
		break
	except ValueError:
		print 'you not input a valid number try again!'

二、拋出異常以及分異常捕獲：

import os,sys
# -*- coding: utf-8 -*-

try:
	raise NameError('nameerror here')
	ff = open("myfile.txt")
	content = ff.readline()
	i = int(content.strip())
except IOError as e:
   print 'IO exception {0}__{1}'.format(e.errno,e.strerror)
except ValueError:
   print 'please input a  number'
except:
   print 'unexcpted exception',sys.exc_info()[0]
   raise

三、用戶自定義異常

# -*- coding: utf-8 -*-

#自定義異常

class MyError(Exception):
	def __init__(self, value):
		self.value = value

	def __str__(self):
			return repr(self.value)
try:
	raise MyError(2*2)
except MyError as e:
		print 'My exception occurred, value:', e.value