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