这个代码模板应该允许您用自定义消息引发异常。

try:
     raise ValueError
except ValueError as err:
    raise type(err)("my message")

try:
    try:
        int('a')
    except ValueError as e:
        raise ValueError('There is a problem: {0}'.format(e))
except ValueError as err:
    print err

打印:

There is a problem: invalid literal for int() with base 10: 'a'

我尝试了这个精简版的@RobinL，效果很好:

try:
    do_something_that_might_raise_an_exception()
except ValueError as e:
    raise ValueError(f'Custom text {e}')

如果你想自定义错误类型，你可以做的一件简单的事情就是基于ValueError定义一个错误类。

Python 3内置异常有strerror字段:

except ValueError as err:
  err.strerror = "New error message"
  raise err

如果你足够幸运只支持python 3。X，这真的变成了一件美丽的事情:)

提高从

我们可以使用raise from链接异常。

try:
    1 / 0
except ZeroDivisionError as e:
    raise Exception('Smelly socks') from e

在这种情况下，调用者将捕获的异常具有引发异常的位置的行号。

Traceback (most recent call last):
  File "test.py", line 2, in <module>
    1 / 0
ZeroDivisionError: division by zero

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

Traceback (most recent call last):
  File "test.py", line 4, in <module>
    raise Exception('Smelly socks') from e
Exception: Smelly socks

注意，底部异常只有我们引发异常的堆栈跟踪。调用者仍然可以通过访问他们捕获的异常的__cause__属性来获得原始异常。

with_traceback

或者你可以使用with_traceback。

try:
    1 / 0
except ZeroDivisionError as e:
    raise Exception('Smelly socks').with_traceback(e.__traceback__)

使用这种形式，调用者将捕获的异常具有原始错误发生位置的回溯。

Traceback (most recent call last):
  File "test.py", line 2, in <module>
    1 / 0
ZeroDivisionError: division by zero

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "test.py", line 4, in <module>
    raise Exception('Smelly socks').with_traceback(e.__traceback__)
  File "test.py", line 2, in <module>
    1 / 0
Exception: Smelly socks

注意，底部的异常中有执行无效除法的行，也有重新引发异常的行。