Python：捕获特定异常

我有这样的代码（Python 2.5，GAE dev服务器）：

所以我在最后一行设置了断点，在调试器下我看到：

"exc"   TokenUpgradeFailed: {'status': 403, 'body': 'html stripped', 'reason': 'Non 200 response on upgrade'}   
"type(exc)" type: <class 'gdata.service.TokenUpgradeFailed'>
"exc is gdata.service.TokenUpgradeFailed"   bool: False 
"exc.__class__" type: <class 'gdata.service.TokenUpgradeFailed'>
"isinstance(exc, gdata.service.TokenUpgradeFailed)" bool: False 
"exc.__class__.__name__"    str: TokenUpgradeFailed 

“exc”令牌升级失败：{'status'：403，'body'：'html stripped'，'reason'：'Non 200 response on upgrade'}
“类型（exc）”类型：
“exc是gdata.service.TokenUpgradeFailed”bool:False
“exc.\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu类”类型：
“isinstance（exc，gdata.service.TokenUpgradeFailed）”bool:False
“exc.\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu

---

我在python异常处理中遗漏了什么？为什么isinstance（exc，gdata.service.TokenUpgradeFailed）为False？

如果您的相对/绝对

import

语句不匹配，则可能发生此错误。如果存在不匹配，则可以在稍微不同的上下文中多次加载目标模块。通常这不是问题，但它确实会阻止来自不同加载模块的类进行相等比较（因此出现异常捕获问题）

错误可能还有其他原因，但我建议仔细检查代码，确保导入

gdata.service

模块的所有内容都明确提到

gdata

包。即使在

gdata

包本身中，使用

服务的每个模块都应该通过
从gdata导入服务
显式地从包中导入，而不是通过相对导入：
导入服务

"exc"   TokenUpgradeFailed: {'status': 403, 'body': 'html stripped', 'reason': 'Non 200 response on upgrade'}   
"type(exc)" type: <class 'gdata.service.TokenUpgradeFailed'>
"exc is gdata.service.TokenUpgradeFailed"   bool: False 
"exc.__class__" type: <class 'gdata.service.TokenUpgradeFailed'>
"isinstance(exc, gdata.service.TokenUpgradeFailed)" bool: False 
"exc.__class__.__name__"    str: TokenUpgradeFailed