当我提出自己的异常作为响应时，如何更轻松地抑制以前的异常？

Question

考虑

try:
   import someProprietaryModule
except ImportError:
   raise ImportError('It appears that <someProprietaryModule> is not installed...')

运行时，如果未安装某些专有模块，则会看到：

(traceback data)
ImportError: unknown module: someProprietaryModule

During handling of the above exception, another exception occurred:

(traceback data)
ImportError: It appears that <someProprietaryModule> is not installed...

也许我不希望出现“在处理上述异常期间...”行（及其上面的行）。我可以这样做：

_moduleInstalled = True
try:
   import someProprietaryModule
except ImportError:
   _moduleInstalled = False
if not _moduleInstalled: 
   raise ImportError('It appears that <someProprietaryModule> is not installed...')

但这感觉有点像黑客。我还能做什么？

Answer 1

在Python 3.3及更高版本中

raise ... from None

可以在这种情况下使用。

try:
   import someProprietaryModule
except ImportError:
   raise ImportError('It appears that <someProprietaryModule> is not installed...') from None

这已经达到了预期的结果。

Answer 2

这可以在 Python 2.7 和 Python 3 中这样完成：

try:
    import someProprietaryModule
except ImportError as e:
    raised_error = e

if isinstance(raised_error, ImportError):
    raise ImportError('It appears that <someProprietaryModule> is not installed...')

Answer 3

您也可以尝试

logging

模块

原答案： 也许我不希望出现“在处理上述异常期间...”行（及其上面的行）。

import logging

try:
    import someProprietaryModule
    
except Exception as e:
    
    if hasattr(e, 'message'):
        logging.warning('python2')
        logging.error(e.message)
        
    else:
        
        logging.warning('python3')
        logging.error('It appears that <someProprietaryModule> is not installed...')

给予

WARNING:root:python3
ERROR:root:It appears that <someProprietaryModule> is not installed...

[Program finished]

编辑：

import logging

class MyExceptionType(Exception):
    """Base class for other exceptions"""
    pass

try:
    from someProprietaryModule import *
except Exception as e:
        logging.warning('python3')
        logging.exception("Failed to import <someProprietaryModule>. Is it installed?", exc_info=False)
        raise MyExceptionType from e

logging.exception

将发出堆栈跟踪以及本地化错误消息，这使得它非常有用。

将异常转换为字符串来打印它会删除 90% 的有用信息。

默默地抑制异常几乎总是一个错误，而且最常见的是枪炮。

编辑2：

import logging

class MyExceptionType(Exception):
    """Base class for other exceptions"""
    pass

try:
    import someProprietaryModule
    
except Exception as e:
    error_message = "Failed to import <someProprietaryModule>. Is it installed?"
    logging.warning('python3')
    logging.error(error_message, exc_info=True)  # Log the stacktrace along with the message
    raise MyExceptionType(error_message) from e

logging.error 调用中的 exc_info 参数设置为 True，允许日志记录模块在日志输出中包含异常信息，包括回溯。 本地化的错误消息存储在变量 error_message 中，这使得代码更具可读性，并且可以在需要时轻松更改。