Python学习 之 异常

#coding:utf8
filename=raw_input("请输入你要操作的文件")
try:
f=open(filename)
print 'hello'
except IOError,msg:
print "你指定的文件不存在"
except NameError,msg:
print "内部变量调用错误"
finally:            #finally
try:     #异常嵌套
f.close()
except NameError,msg:
pass
if filename=='hello':
raise NameError("nothing!!!")    #抛出异常