以下是我在个人项目中使用的方法(我相信有足够的理由不在产品代码中这样做):

try:
    #something hazardous
except Exception as e:
    insightful_message = "shouldn't have done that"
    amended_args = tuple([f'{e.args[0]}\n{insightful_message}', *e.args[1:]])
    e.args = amended_args
    raise

代码(1)拦截错误;(2)创建错误的.args属性的副本，这是一个元组，假定在索引0处包含一个错误消息，使用列表理解实现;(3)在错误消息后追加换行符和自定义消息;(4)使用。args附加到副本的任何附加项 拆包;(5)将副本转换为元组;最后(6)用修改后的副本替换。args。

这些操作大多是为了避免.args元组的不可变性。

如果你来这里寻找Python 3的解决方案，手册上说:

当引发一个新的异常时(而不是使用一个简单的raise来重新引发当前正在处理的异常)，隐式异常上下文可以通过使用from和raise来补充显式原因:

raise new_exc from original_exc

例子:

try:
    return [permission() for permission in self.permission_classes]
except TypeError as e:
    raise TypeError("Make sure your view's 'permission_classes' are iterable. "
                    "If you use '()' to generate a set with a single element "
                    "make sure that there is a comma behind the one (element,).") from e

最后是这样的:

2017-09-06 16:50:14,797 [ERROR] django.request: Internal Server Error: /v1/sendEmail/
Traceback (most recent call last):
File "venv/lib/python3.4/site-packages/rest_framework/views.py", line 275, in get_permissions
    return [permission() for permission in self.permission_classes]
TypeError: 'type' object is not iterable 

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
    # Traceback removed...
TypeError: Make sure your view's Permission_classes are iterable. If 
     you use parens () to generate a set with a single element make 
     sure that there is a (comma,) behind the one element.

将一个完全无描述的TypeError转换为一个带有解决方案提示的漂亮消息，而不会搞乱原始异常。

我将提供一段我经常使用的代码片段，每当我想向异常添加额外信息时。我在Python 2.7和3.6中都可以工作。

import sys
import traceback

try:
    a = 1
    b = 1j

    # The line below raises an exception because
    # we cannot compare int to complex.
    m = max(a, b)  

except Exception as ex:
    # I create my  informational message for debugging:
    msg = "a=%r, b=%r" % (a, b)

    # Gather the information from the original exception:
    exc_type, exc_value, exc_traceback = sys.exc_info()

    # Format the original exception for a nice printout:
    traceback_string = ''.join(traceback.format_exception(
        exc_type, exc_value, exc_traceback))

    # Re-raise a new exception of the same class as the original one, 
    # using my custom message and the original traceback:
    raise type(ex)("%s\n\nORIGINAL TRACEBACK:\n\n%s\n" % (msg, traceback_string))

上面的代码产生如下输出:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-6-09b74752c60d> in <module>()
     14     raise type(ex)(
     15         "%s\n\nORIGINAL TRACEBACK:\n\n%s\n" %
---> 16         (msg, traceback_string))

TypeError: a=1, b=1j

ORIGINAL TRACEBACK:

Traceback (most recent call last):
  File "<ipython-input-6-09b74752c60d>", line 7, in <module>
    m = max(a, b)  # Cannot compare int to complex
TypeError: no ordering relation is defined for complex numbers

我知道这与问题中提供的例子有一点偏差，但我希望有人觉得它有用。

在PEP 678中，本机支持向异常添加注释:

try:
  raise TypeError('bad type')
except Exception as e:
  e.add_note('Add some information')
  raise

呈现为:

Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
TypeError: bad type
Add some information

我跳它可以取代史蒂夫霍华德的解决方案，不幸的是，它不给用户任何控制如何格式化最终的异常(例如，不能在异常之前添加一个注释，如:'错误在fn: {original_exc}')

如果想要对回溯进行更多控制，可以使用https://github.com/google/etils:

from etils import epy

with epy.maybe_reraise('Error in fn: '):
  fn()

Or:

try:
  fn()
except Exception as e:
  epy.reraise(e, suffix='. Did you mean y ?')

以下是我在个人项目中使用的方法(我相信有足够的理由不在产品代码中这样做):

try:
    #something hazardous
except Exception as e:
    insightful_message = "shouldn't have done that"
    amended_args = tuple([f'{e.args[0]}\n{insightful_message}', *e.args[1:]])
    e.args = amended_args
    raise

代码(1)拦截错误;(2)创建错误的.args属性的副本，这是一个元组，假定在索引0处包含一个错误消息，使用列表理解实现;(3)在错误消息后追加换行符和自定义消息;(4)使用。args附加到副本的任何附加项 拆包;(5)将副本转换为元组;最后(6)用修改后的副本替换。args。

这些操作大多是为了避免.args元组的不可变性。

与之前的答案不同，这适用于非常糟糕的__str__异常。 但是，它确实修改了类型，以便剔除无用的__str__实现。

我仍然希望找到一个不修改类型的额外改进。

from contextlib import contextmanager
@contextmanager
def helpful_info():
    try:
        yield
    except Exception as e:
        class CloneException(Exception): pass
        CloneException.__name__ = type(e).__name__
        CloneException.__module___ = type(e).__module__
        helpful_message = '%s\n\nhelpful info!' % e
        import sys
        raise CloneException, helpful_message, sys.exc_traceback


class BadException(Exception):
    def __str__(self):
        return 'wat.'

with helpful_info():
    raise BadException('fooooo')

原始的回溯和类型(名称)被保留。

Traceback (most recent call last):
  File "re_raise.py", line 20, in <module>
    raise BadException('fooooo')
  File "/usr/lib64/python2.6/contextlib.py", line 34, in __exit__
    self.gen.throw(type, value, traceback)
  File "re_raise.py", line 5, in helpful_info
    yield
  File "re_raise.py", line 20, in <module>
    raise BadException('fooooo')
__main__.BadException: wat.

helpful info!